The cheapest AI voice agent in 2026: published per-minute prices, compared

Among managed platforms with published, computable pricing, ThunderPhone Spark has the lowest complete per-minute engine rate we found as of September 10, 2026. Its 2¢ per minute includes speech recognition, the language model, and voice. Plivo Voice AI is the closest competitor at $0.0355/minute for US inbound local calls, although its LLM inclusion is unconfirmed. Plivo’s combined rate includes carrier telephony; ThunderPhone’s engine rate excludes it. Plivo pricing and US voice pricing, accessed 2026-09-10. As illustrative arithmetic, lean DIY component stacks compute to roughly the same floor before engineering work. Call length, language, telephony, and configuration can reorder the results, so rerun the arithmetic for your workload.

“Complete engine rate” matters here. Spark covers the voice-AI engine, not every possible cost of placing a phone call. Telephony depends on setup, selected premium voice or language paths can add up to 3¢ per minute, and optional features have published surcharges. The claim is therefore narrower, and more useful, than saying one product is always cheapest.

Why “cheapest voice AI” claims are slippery

An AI phone agent platform’s per-minute headline may describe an entire engine, one infrastructure component, a hosting fee before provider bills, or an overage after a monthly allowance. Other services bill per call or per unique customer, making direct per-minute comparisons impossible without assumptions. Enterprise products may publish only a contract minimum.

Those differences are large enough to reverse a ranking. Vapi’s $0.05 per minute is hosting before speech, model, voice, and telephony costs, while Telnyx’s $0.05 covers orchestration, speech-to-text, and text-to-speech but leaves model tokens and telephony on top. Vapi pricing and Telnyx pricing, accessed 2026-09-10. A subscription can look inexpensive until overage dominates, while a higher per-minute tier can still cost more after its platform fee.

For the deeper taxonomy, see how voice AI platforms price and the AI phone-agent cost guide. When choosing an AI calling platform, the table below keeps each vendor’s billing unit intact before normalizing one scenario.

Published pricing at a glance

Computable configurations appear first, ordered by their September 10 usage floor before fixed fees; incomplete subtotals follow separately. Plivo and Cartesia remain conditional on the inclusion caveats above. Deepgram’s later rate remains below Retell’s floor.

Phonely’s discrepancy deserves explicit treatment: its plan cards say Starter includes 200 minutes and Professional includes 650, while the comparison table on the same page says 250 and 750. Its FAQ also says Starter supports up to 50 calls while the card estimates about 100. Confirm the live allowance before buying. Phonely pricing, accessed 2026-09-01.

For details, read Plivo Voice AI pricing, Deepgram Voice Agent pricing, Cartesia Line pricing, and Twilio ConversationRelay pricing. Compare ThunderPhone vs. Plivo and ThunderPhone vs. Telnyx. The Voice AI Price Index provides the dataset in JSON and CSV.

Worked example: 10,000 connected minutes

Every computation in this section is illustrative planning arithmetic, not a quote. Use the reference workload: 2,000 calls × 5 connected minutes = 10,000 connected minutes in a month. Assume one primary included language, no transfers, hold, voicemail, or optional add-ons, one phone number, and no more than 10 concurrent calls. Distribute traffic evenly enough to fit the stated tier limits. Fixed fees and number rental are added only where explicitly shown. For Deepgram, assume WebSocket connection time equals connected call time.

• ThunderPhone Spark: 10,000 × $0.02 = $200 for the engine. A selected premium voice or language path at the maximum surcharge would add up to 10,000 × $0.03 = $300; telephony remains setup-dependent.
• Plivo Voice AI: 10,000 × ($0.03 agent + $0.0055 inbound local) = $355; add $0.50 local-number rental = $355.50. Outbound local: 10,000 × ($0.03 + $0.0115) + $0.50 = $415.50. LLM inclusion remains unconfirmed. Plivo pricing and US voice pricing, accessed 2026-09-10.
• ThunderPhone Spark with Plivo SIP: US local inbound PSTN: 10,000 × ($0.02 engine + $0.0055 Plivo inbound local) = $255; add $0.50 local-number rental = $255.50. If the manual-SIP route also bills Plivo's $0.0033/min SIP leg, the total is $288.50; the published pages do not establish whether both legs bill, so confirm the carrier configuration. Keep Plivo telephony and connect through manual SIP. Plivo US voice pricing, accessed 2026-09-10.
• Telnyx: using the components behind its own example, 10,000 × ($0.05 + $0.0032 + $0.0032) = $564; add $1 number rental = $565. LLM usage is illustrative and bills per token. Telnyx pricing, accessed 2026-09-10.
• Deepgram Voice Agent API: through September 12, 2026, 10,000 × $0.056 = $560 for Standard PAYG. Via Twilio, 10,000 × ($0.056 + $0.0085 + $0.0044) + $1.15 number rental = $690.15. From September 13, 10,000 × $0.075 = $750 for the engine; the same carrier setup gives 10,000 × ($0.075 + $0.0085 + $0.0044) + $1.15 = $880.15. Deepgram pricing, Twilio US voice pricing, and Media Streams pricing, accessed 2026-09-10.
• Cartesia Line: 10,000 × ($0.06 agent + $0.014 telephony) = $740, plus the applicable plan fee. LLM usage is temporarily free for UI-created agents; the offer’s end date is not published. The Free plan allows 8 concurrent calls; Pro allows 12 at $5/month, giving $740 + $5 = $745 for the assumed peak. Confirm agent-minute eligibility and any number charges. Cartesia pricing, accessed 2026-09-10.
• Retell AI: 10,000 × ($0.055 infrastructure + $0.015 voice + $0.003 LLM + $0.015 telephony) = $880, before number rental and add-ons. Its advertised $0.07–$0.31 range is not a complete call-cost range. Retell pricing, accessed 2026-09-10.
• Twilio ConversationRelay: 10,000 × ($0.07 relay + $0.0085 inbound local) + $1.15 number rental = $786.15 plus LLM costs. Built-in STT/TTS inclusion and premium-voice surcharges are unconfirmed. ConversationRelay pricing and US voice pricing, accessed 2026-09-10.
• ElevenLabs Agents: Scale’s $299 includes 3,738 minutes; $299 + (10,000 − 3,738) × $0.08 = $799.96, before LLM and telephony. With Twilio inbound, $799.96 + 10,000 × $0.0085 + $1.15 = $886.11 plus LLM. This assumes standard overage; confirm the plan supports the assumed peak. Excess concurrency raises additional-minute pricing to $0.16. ElevenLabs Agents pricing and Twilio US voice pricing, accessed 2026-09-10.
• Callplane: 10,000 × $0.03 = $300 platform cost. BYO totals $300 + provider bills; Cloud totals $300 + 1.15 × provider costs. Managed-provider unit rates are not published, so a complete total is not computable. Callplane pricing, accessed 2026-09-10.
• Vapi: hosting alone is 10,000 × $0.05 = $500, before speech, model, voice, and telephony costs. A complete total cannot be computed from the public page. Vapi pricing, accessed 2026-09-10.
• Bland AI: Start is 10,000 × $0.14 + $0 = $1,400; Build is 10,000 × $0.12 + $299 = $1,499, before telephony. Start is cheapest only if the 2,000 monthly calls stay within its 100-calls-per-day and 10-concurrent-call limits. Scale is no longer published; Enterprise is custom. Bland pricing, accessed 2026-09-10.
• Phonely Starter on monthly billing: using the comparison table’s 250 included minutes, $50 + (10,000 − 250) × $0.25 = $2,487.50. Using the plan card’s newer 200-minute figure, $50 + (10,000 − 200) × $0.25 = $2,500. The source disagrees with itself, so treat this as a range and confirm the allowance. Phonely pricing, accessed 2026-09-01.
• Smith.ai AI Receptionist: the five-minute call assumption gives 10,000 ÷ 5 = 2,000 calls. The published 500-call Enterprise option has a package-effective rate of $800 ÷ 500 = $1.60/call. Including overage, $800 + (2,000 − 500) × $2.10 = $3,950. This conversion depends completely on average call length. Smith.ai AI Receptionist pricing, accessed 2026-09-01.
• Goodcall: minutes do not determine the bill. If those 2,000 calls come from 1,500 unique customers, Scale computes as $249 + (1,500 − 500) × $0.50 = $749. Fewer repeat callers would cost more; more repeat calls from the same people would not add unique customers. Goodcall pricing, accessed 2026-09-01.
• Synthflow: the published $30,000 annual contract floor does not disclose how many minutes it buys, so this workload has no public total. Synthflow pricing, accessed 2026-09-01.

In this defined scenario, ThunderPhone Spark’s published engine arithmetic is lowest among the managed platforms with comparable, computable usage prices. That is not a universal ranking. Different languages, call lengths, call distributions, configurations, and telephony arrangements can change both eligibility and ordering.

What the cheapest DIY voice AI actually costs

The attention-grabbing DIY floor is real, but it needs attribution. The open-source hypercheap-voiceAI repository claims costs “as low as $0.28 per hour ($0.0046 per minute)” (the repository's own rounding; $0.28 ÷ 60 is about $0.0047) and a typical $0.25–$0.35 per session hour. Those are third-party project claims, not verified vendor list prices, and some underlying speech-recognition figures could not be independently checked. hypercheap-voiceAI, accessed 2026-09-01.

Public component prices establish a more reproducible floor. Streaming speech-to-text has list-price reference points around $0.0025–$0.006 per minute: an illustrative conversion, not a quote, is AssemblyAI’s $0.15/hour ÷ 60 = $0.0025/minute, while OpenAI lists $0.003–$0.006/minute and Deepgram lists $0.0048 promotional and $0.0077 regular pricing. AssemblyAI pricing, OpenAI API pricing, and Deepgram pricing, accessed 2026-09-01.

LLM inference adds roughly $0.001–$0.01 per conversation minute as an illustrative planning estimate, not a quote, depending on model choice and context growth. That range rests on published token prices and conversation-token assumptions, not a flat per-minute tariff. OpenAI API pricing, Google Gemini API pricing, Together AI pricing, and Inworld’s voice-agent cost model, accessed 2026-09-01.

Text-to-speech list prices around $4–$30 per million characters convert, at about 1,000 generated characters per speaking minute, to an illustrative $0.004–$0.03 per generated-speech minute, not a quote; only the agent’s speaking share is billed. Google Cloud TTS pricing, Amazon Polly pricing, and Inworld TTS pricing, accessed 2026-09-01. Hosted orchestration can add $0.01/minute, while US telephony reference points run from $0.0032/minute inbound on Telnyx to $0.018/minute PSTN on Daily/Pipecat Cloud. LiveKit pricing, Telnyx SIP pricing, and Daily/Pipecat pricing, accessed 2026-09-01.

One lean-stack illustration makes the floor concrete: $0.0025 STT + $0.001 estimated LLM + ($0.004 TTS × 50% speaking share) + $0.01 orchestration + $0.0032 telephony = $0.0187 per conversation minute, or 1.87¢. This is illustrative planning arithmetic, not a quote, and it mixes category-floor assumptions that may not meet a particular quality, latency, reliability, or geography requirement. Lean combinations therefore land around 1–4¢ per minute before engineering. AssemblyAI pricing, OpenAI API pricing, Google Cloud TTS pricing, LiveKit pricing, and Telnyx SIP pricing, accessed 2026-09-01.

Deepgram's Nova-3 streaming STT figures were re-confirmed 2026-09-10 at $0.0048/minute promotional and $0.0077/minute regular pricing.

The missing line items are engineering time, monitoring, redundancy, concurrency headroom, incident response, compliance work, and support. A component demo and a production phone system are different deliverables. See the full voice AI cost breakdown and ThunderPhone versus building your own before treating raw API spend as total cost.

How a managed 2¢-per-minute rate compares

ThunderPhone Spark’s 2¢ engine rate includes speech recognition, a language model, and voice without requiring the buyer to assemble those services. It is prepaid and pay as you go, with no subscription, seat fee, or platform fee. Signing up and building are free; making real calls requires a payment method and at least $3.00 in prepaid balance, and funds do not expire. See ThunderPhone pricing explained.

The boundary is equally important. Telephony is not part of the engine rate and depends on whether a customer uses an imported VoIP/SIP number or a ThunderPhone number. A selected premium voice or language path can add up to 3¢ per minute, and optional features such as supervision, long prompts, ThunderPhone-number usage, or live transcripts can add to the configured rate. The builder shows the all-in per-minute engine rate for the exact configuration before calls run, while Billing History itemizes calls afterward.

At very low volume, a flat subscription with bundled numbers may be simpler even when its unit economics are higher. Phonely Starter, for example, bundles multiple numbers with its monthly plan, subject to the live-page allowance discrepancy noted above. At high volume, lower rates attached to platform fees or custom commitments can amortize differently. Price convenience, operational limits, and total invoices, not just the smallest headline.

FAQ

What is the cheapest AI voice agent platform?

Among the managed platforms with published, computable pricing reviewed here, ThunderPhone Spark has the lowest complete base-engine rate at 2¢ per minute. That rate includes speech recognition, the language model, and voice. Telephony and selected options can add cost, and changes in language, configuration, or call pattern can reorder the comparison.

Can you really run an AI voice agent for 2 cents a minute?

Yes, ThunderPhone publishes a 2¢-per-minute Spark engine rate, and DIY component arithmetic can approach the same level. Spark includes the three core engine components in one rate; it does not include setup-dependent telephony or every optional add-on. The lean DIY example above computes to 1.87¢ per conversation minute, but it is illustrative planning arithmetic, not a quote, and excludes engineering and operations.

Is building your own voice agent cheaper than a platform?

It can be cheaper in raw API spend, but not necessarily in total cost. A community repository claims as little as $0.0046 per minute, while reproducible vendor list-price combinations suggest a lean 1–4¢ component floor. Engineering, monitoring, redundancy, concurrency, compliance, and support sit outside that number. hypercheap-voiceAI, AssemblyAI pricing, Google Cloud TTS pricing, LiveKit pricing, and Telnyx SIP pricing, accessed 2026-09-01.

What hidden costs make “cheap” voice AI expensive?

Add-on stacking, overage, platform fees, concurrency, telephony, and compliance can outweigh the headline. Retell lists several $0.005/minute add-ons, $0.01/minute PII removal, and $0.10/minute AI quality assurance after its free allowance. Retell pricing, accessed 2026-09-01. Added concurrency is $8 per concurrent call monthly. Retell pricing, accessed 2026-09-10. Phonely displays Starter overage at $0.25/minute monthly and $0.35/minute under annual billing. Phonely pricing, accessed 2026-09-01. Bland's Build platform fee is $299 monthly; Start has no platform fee, and the former Scale tier is no longer published. Bland pricing, accessed 2026-09-10. Vapi lists HIPAA at $2,000/month and zero data retention at $1,000/month. Vapi pricing, accessed 2026-09-10.

How much does 10,000 minutes a month cost?

For the defined workload, ThunderPhone Spark costs $200 for the engine; vendor totals depend on included services, allowances, and call patterns. These are illustrative calculations, not quotes. Assume 2,000 five-minute calls, one primary included language, one phone number, no transfers, hold, voicemail, or optional add-ons, and at most 10 concurrent calls.

• ThunderPhone Spark: $200 for the engine, with setup-dependent telephony extra. ThunderPhone pricing, accessed 2026-09-10.
• Plivo Voice AI: $355.50, including US inbound local telephony and one local number; LLM inclusion remains unconfirmed. Plivo pricing and US voice pricing, accessed 2026-09-10.
• Telnyx: $565, including one number, using the per-token LLM assumptions behind its published example. Telnyx pricing, accessed 2026-09-10.
• Deepgram Standard PAYG: $690.15 through September 12, 2026; $880.15 from September 13, including Twilio inbound local telephony, Media Streams, and one number. This assumes WebSocket connection time equals connected call time. Deepgram pricing, Twilio US voice pricing, and Media Streams pricing, accessed 2026-09-10.
• Retell: $880 configured floor, including the cheapest listed LLM, voice, infrastructure, and telephony, before number rental and add-ons. Retell pricing, accessed 2026-09-10.
• Bland Start: $1,400, before telephony, if traffic fits its 100-calls-per-day and 10-concurrent-call limits. Bland pricing, accessed 2026-09-10.
• Phonely Starter: $2,487.50–$2,500 on monthly billing, depending on whether its 250-minute comparison-table allowance or 200-minute plan-card allowance applies. Confirm the allowance because the page disagrees with itself. Phonely pricing, accessed 2026-09-01.
• Smith.ai AI Receptionist: $3,950, using 2,000 five-minute calls and its 500-call Enterprise option with extra-call charges. Smith.ai AI Receptionist pricing, accessed 2026-09-01.
• Goodcall: $749, assuming those 2,000 calls come from 1,500 unique customers on Scale. Repeat calls from the same customers do not add unique customers. Goodcall pricing, accessed 2026-09-01.

Sources and freshness

The first-party pricing re-check is dated September 10, 2026; ThunderPhone facts were verified that day. Phonely, Smith.ai, Goodcall, and Synthflow figures retain their 2026-09-01 verification. The hypercheap-voiceAI numbers are explicitly labeled as third-party repository claims. Inclusion uncertainties are identified beside the relevant rates.

• ThunderPhone pricing, accessed 2026-09-10.
• Plivo pricing and US voice pricing, accessed 2026-09-10.
• Telnyx Voice AI pricing and SIP pricing, accessed 2026-09-10.
• Deepgram pricing, accessed 2026-09-10.
• Cartesia pricing, accessed 2026-09-10.
• Twilio ConversationRelay pricing, US voice pricing, and Media Streams pricing, accessed 2026-09-10.
• Callplane pricing, accessed 2026-09-10.
• ElevenLabs Agents pricing, accessed 2026-09-10.
• Retell pricing, Vapi pricing, and Bland pricing, accessed 2026-09-10.
• Phonely pricing, Smith.ai AI Receptionist pricing, Goodcall pricing, and Synthflow pricing, accessed 2026-09-01; not re-verified in this update.
• hypercheap-voiceAI, accessed 2026-09-01; third-party repository claims.
• AssemblyAI pricing, OpenAI API pricing, and Deepgram pricing, accessed 2026-09-01.
• Google Gemini API pricing, Together AI pricing, and Inworld’s voice-agent cost model, accessed 2026-09-01.
• Google Cloud TTS pricing, Amazon Polly pricing, and Inworld TTS pricing, accessed 2026-09-01.
• LiveKit pricing, Telnyx SIP pricing, and Daily/Pipecat pricing, accessed 2026-09-01.

This comparison is documentation-based; no vendor accounts, invoices, or live calls were tested. Prices and plan terms change, so verify the live pages and rerun the arithmetic for your own call length, language, telephony, and configuration before relying on any result.