Vapi vs Retell vs Bland vs Synthflow in 2026: The Real All-In Per-Minute Cost of Voice AI

All four platforms advertise a per-minute rate. None of those numbers is what you actually pay. Here is the honest 2026 all-in math, per sales use-case, with latency and telephony detail.

Last verified April 2026

$0.25-$0.33/min

Vapi all-in typical

$0.07-$0.20/min

Retell all-in typical

$0.10-$0.30/min

Bland all-in typical

$0.08-$0.23/min

Synthflow plan or usage

§Why Voice AI Is a Four-Component Bill

Every voice AI platform advertises a headline per-minute rate. That rate almost never reflects total cost, because a complete voice agent requires four components, and platforms expose the bundle differently. Before comparing Vapi to Retell to Bland, you need to know which components each includes and which you are bringing yourself.

STT

Speech-to-Text

Deepgram, Whisper, AssemblyAI

$0.005-$0.01/min

LLM

Language Model

GPT-4, Claude 3, Llama 3

$0.05-$0.15/min

TTS

Text-to-Speech

ElevenLabs, PlayHT, Cartesia

$0.02-$0.10/min

Telephony

Phone Network

Twilio, Telnyx, bundled PSTN

$0.01-$0.03/min

§Vapi - Most Flexible Pipeline

Platform rate

$0.05/min

Plus your STT + LLM + TTS + Telephony

+$0.20-$0.28

All-in typical (sales use case)

$0.25-$0.33/min

Vapi is the most developer-friendly voice AI platform with the strongest community and the most flexible pipeline. You bring your own STT (Deepgram is the most common choice at $0.0043/min), your LLM (GPT-4 Turbo adds ~$0.10-$0.15/min at typical sales-call token usage), your TTS (ElevenLabs adds $0.02-$0.10/min), and telephony (Twilio SIP at $0.01-$0.02/min). Vapi's platform fee of $0.05/min orchestrates all four.

Strengths: Maximum flexibility in pipeline composition; strongest developer community and documentation; easiest to swap components (e.g., replace ElevenLabs with Cartesia for lower latency); integrations with most CRM and webhook targets.

Weaknesses: All-in cost is the highest of the group; compliance setup (TCPA consent capture, GDPR recording disclosure) is entirely your responsibility; no managed telephony means more DevOps overhead.

§Retell AI - Often Cheapest All-In

Platform + managed telephony

$0.07/min bundled

Plus your LLM (+ TTS if needed)

+$0.00-$0.13

All-in typical

$0.07-$0.20/min

Retell's $0.07/min includes STT, TTS, and telephony. You bring your LLM. Using a cost-optimised LLM (Llama 3 via Groq or Claude Haiku), the all-in rate can stay at $0.10-$0.12/min - materially cheaper than Vapi for the same use case. Retell reports inbound latency of 250-400ms, which is best-in-class among the four platforms.

Strengths: Often cheapest all-in for standard sales deployments; best-in-class latency for inbound voice; managed telephony reduces DevOps overhead; growing API and webhook ecosystem.

Weaknesses: Less pipeline flexibility than Vapi (fewer TTS and STT options); smaller developer community; compliance responsibility still falls on you.

§Bland AI + Synthflow

Bland AI

$0.09-$0.14/min base + plan subscription

Bland changed its pricing model in December 2025 to a subscription-plus-usage structure. Plans include a set number of minutes; overages bill at the per-minute rate. Transfer charges and voice-cloning add-ons add to the total. All-in cost is harder to forecast than Vapi or Retell - $0.10-$0.30/min depending on plan usage pattern and extras. Good out-of-box voice quality and simple onboarding.

Weakness: plan overage math is complex; December 2025 pricing change caught some existing customers off-guard at renewal.

Synthflow

$375-$900/mo plan or $0.08/min usage

Synthflow offers plan-based pricing (Pro: $375/month for 2,000 minutes = $0.19/min equivalent; Growth: $900/month for 4,000 minutes = $0.23/min) and a usage-based option ($0.08/min, $0.07/min enterprise) that is all-inclusive. Synthflow positions as the "simplest end-to-end" alternative for non-developer teams. Its flow builder is simpler than Vapi's but less powerful for complex conversation logic.

Strength: accessible to non-developers; no component assembly required.

§Platform Comparison Table

Platform	Advertised	All-in typical	Latency	Telephony	Best for
Vapi	$0.05/min platform	$0.25-$0.33/min	300-600ms	BYOT (Twilio, Telnyx)	Maximum flexibility; developer-first
Retell AI	$0.07/min bundled	$0.07-$0.20/min	250-400ms (best)	Managed (included)	Cheapest all-in; inbound qualification
Bland AI	$0.09-$0.14/min + plan	$0.10-$0.30/min	300-500ms	Included	Simple onboarding; good voice quality
Synthflow	$375-$900/mo plan or $0.08/min	$0.08-$0.23/min	400-600ms	Included	Non-developer teams; end-to-end managed
ElevenLabs Conversational	From $0.05/min TTS	Add STT + LLM + telephony	Improving in 2026	BYOT	Highest voice naturalness
PlayHT Conversational	$0.01-$0.04/min TTS	Add STT + LLM + telephony	Competitive	BYOT	Competitive TTS pricing
Deepgram Voice Agent	$0.0043/min STT	Add LLM + TTS + telephony	Low-latency STT	BYOT	STT-first use cases; lowest STT rate

§Sales Use-Case Sizing

Inbound qualification

Low risk

3-min avg call, 500 calls/month = 1,500 minutes

Retell

$105/mo (1,500 x $0.07)

Vapi

$420/mo (1,500 x $0.28)

Bland

$180/mo (1,500 x $0.12)

Legal note: Low risk (inbound initiated)

Outbound appointment confirmation

Moderate risk

1-min avg call, 2,000 calls/month = 2,000 minutes

Retell

$140/mo (2,000 x $0.07)

Vapi

$560/mo (2,000 x $0.28)

Bland

$240/mo (2,000 x $0.12)

Legal note: Moderate risk (prior relationship, not cold)

Outbound cold calling

LEGAL RISK

2-min avg call, 5,000 calls/month = 10,000 minutes

Retell

$1,000/mo (10,000 x $0.10)

Vapi

$3,300/mo (10,000 x $0.33)

Bland

$1,200-$2,500/mo

Legal note: HIGH RISK: TCPA requires prior express consent for AI voice

§Compliance Checklist

Critical: TCPA Prior Consent for Outbound AI Voice

FCC Declaratory Ruling 24-17 (adopted 8 February 2024) classified AI-generated voices as "artificial or prerecorded voice" under the TCPA. Outbound AI voice calls without prior express consent are illegal in the US. This applies to Vapi, Retell, Bland, and Synthflow when used for outbound cold calling. Prior express written consent is required for B2C marketing calls.

Full legal compliance guide →

Low

Inbound US call with AI voice agent

Lead initiated; AI disclosure required at call start; CIPA recording disclosure for California

Moderate

Outbound appointment confirmation (known customer)

Prior business relationship may support; get legal opinion on 'established business relationship' scope in your state

Illegal

Outbound AI cold call (no prior consent)

TCPA violation; prior express consent required before placing AI voice calls

CIPA

Recording any call (US, any AI)

All-party consent required for California-resident callers; AI recording may be subject to Ambriz v. Google CIPA theory

GDPR

AI recording or transcription (EU caller)

Affirmative consent required; 'this call may be recorded' notification alone is insufficient under GDPR Article 6(1)(a)

§FAQ

How much does Vapi cost per minute?

Vapi's platform rate is $0.05/minute, but that is not the total cost. You also pay for STT (Deepgram: ~$0.005-$0.01/min), your LLM (GPT-4 level: $0.10-$0.15/min at sales-call token volumes), TTS (ElevenLabs: $0.02-$0.10/min), and telephony (Twilio/Telnyx: $0.01-$0.03/min). All-in for a typical sales use case: $0.25-$0.33/minute.

Vapi vs Retell - which is cheaper all-in?

Retell is almost always cheaper all-in. Retell's $0.07/min includes STT, TTS, and managed telephony; you only add your LLM. With a cost-optimised LLM (Llama 3 via Groq or Claude Haiku), Retell all-in runs $0.10-$0.12/min vs Vapi's $0.25-$0.33/min. Vapi is more flexible (better pipeline composition, larger community) but costs more.

Is AI cold calling legal with Vapi or Retell?

Not without prior express consent. The FCC's Declaratory Ruling 24-17 (February 2024) classified AI-generated voices as artificial/prerecorded under the TCPA. Outbound AI cold calls without prior express written consent for marketing purposes are a TCPA violation. This applies to Vapi, Retell, Bland, and Synthflow. Consult qualified counsel for your specific use case before deploying outbound voice AI.

What is the latency of Retell AI?

Retell AI reports 250-400ms end-to-end latency for inbound voice qualification use cases, which is best-in-class among the major platforms as of April 2026. Vapi typically runs 300-600ms; Bland and Synthflow 300-600ms. Latency below 500ms is generally acceptable for natural conversation; above 600ms users start to notice pauses.

Can I build an AI cold caller with Vapi legally?

You can build it technically. Whether you can operate it legally in the US depends on your consent infrastructure. The FCC (Ruling 24-17, February 2024) requires prior express consent before placing AI voice calls to any number. For B2C marketing calls, prior express written consent is required. Without a robust consent-capture mechanism linked to every number you dial, outbound AI cold calling in the US is a TCPA violation. See the full legal guide.

TCPA + CIPA legal guide →Pipeline generation use cases →Voice AI cost calculator →