Retell AI vs Synthflow AI
Synthflow AI publishes its pricing; Retell AI does not.
Both pages checked by August 19, 2026
- Retell AIAI only
- Pricing not published
- no published plan
- Developer-oriented platform to build, test, deploy and monitor AI voice and chat agents, billed a la carte per minute: a Retell voice-infrastructure rate plus a separately priced text-to-speech voice, a separately priced LLM and separately priced telephony.
- Synthflow AIAI only
- $2500/mo
- Enterprise plan
- Enterprise voice AI platform with in-house telephony for automating inbound and outbound calls, sold through sales-scoped contracts rather than published self-serve plans, with the agent designed, tested and launched by the customer in Synthflow's Flow Designer or Prompt Builder.
The differences that matter
- Synthflow AI publishes prices. Retell AI makes you ask.
Feature by feature
| Capability | Retell AI | Synthflow AI |
|---|---|---|
| Live transfer | Yes | Yes |
| Books appointments | Yes | Yes |
| Text follow-up | Yes | Yes |
| Outbound calls | Yes | Yes |
| Spanish | Yes | Yes |
| Human backup | No | No |
| Call recordings | Yes | Yes |
| Transcripts | Yes | Yes |
| Spam screening | unstated | unstated |
| Custom voice | Yes | Yes |
| API | Yes | Yes |
"unstated" means the vendor doesn't claim it in their own documentation. It is not the same as no — it means nobody will put it in writing.
Retell AI plans
| Plan | Published price | Includes | Over that |
|---|---|---|---|
| Pay-as-you-go | $0.07-$0.31/min for AI Voice Agents | — | — |
| Enterprise | Custom Pricing for AI Voice Agents | — | — |
Synthflow AI plans
| Plan | Published price | Includes | Over that |
|---|---|---|---|
| Enterprise | Enterprise contracts start at $30,000 annually(annual billing) | — | — |
Retell AI sources
- Pricing page (voice infra, TTS, LLM standard/fast tiers, speech-to-speech, telephony, add-ons, monthly subscription items, billing mechanics FAQ)retellai.com · read August 19, 2026
- Docs: Build your first phone agent in 15 minutes ($10 free trial credits, no payment method required; build-from-scratch vs template; free web-call testing)docs.retellai.com · read August 19, 2026
- Docs: Introduction (platform description, agent types, CRM/Cal.com tools, SDKs and MCP server)docs.retellai.com · read August 19, 2026
- Docs: Billing (credit-based vs legacy monthly billing, $10 free trial credits, which items are metered vs subscription)docs.retellai.com · read August 19, 2026
- Docs: Supported languages by provider (TTS and ASR coverage tables)docs.retellai.com · read August 19, 2026
- Docs index (transfer call cold/warm/agentic warm, Cal.com check-availability and booking, SMS node, batch calls, custom voices and voice clones, call recordings and transcripts, data retention, Twilio/Telnyx/Vonage SIP import, international calling)docs.retellai.com · read August 19, 2026
- Homepage (positioning, target industries, "Try For Free" with $10 of free usage)retellai.com · read August 19, 2026
- Terms of Service (entity and address: Retell AI Inc., 540 Price Avenue, Redwood City, CA 94063; Delaware jurisdiction)retellai.com · read August 19, 2026
Synthflow AI sources
- Pricing page (Enterprise-only; "Enterprise contracts start at $30,000 annually"; scoping variables and contract inclusions)synthflow.ai · read August 19, 2026
- Homepage (positioning, target industries, free-trial FAQ answer and PAYG statement)synthflow.ai · read August 19, 2026
- Docs: Billing Overview ("Synthflow uses sales-led pricing", legacy billing labels, do-not-quote-from-docs warning)docs.synthflow.ai · read August 19, 2026
- Docs: Usage and Billing (per-second measurement, minute aggregation with carryover, flat 5s for no-answer, call-state billing table, chat at 5 AI messages per minute, allowances and carryover)docs.synthflow.ai · read August 19, 2026
- Docs: Concurrency (concurrency vs CAPS, "Scoped with Synthflow", no published defaults)docs.synthflow.ai · read August 19, 2026
- Docs: Languages (transcribers Deepgram and Synthflow STT, full supported-language list)docs.synthflow.ai · read August 19, 2026
- Docs: Integrations overview (GoHighLevel, Salesforce, HubSpot, Zendesk, Freshworks, Cal.com, Stripe, WhatsApp, ElevenLabs, Zapier, Make, Bubble, OpenAI/Anthropic/Azure BYOK, telephony)docs.synthflow.ai · read August 19, 2026
- Docs: Logs (call recordings and transcripts, live monitoring, CSV export, opt-out of saving recordings)docs.synthflow.ai · read August 19, 2026
- Docs: Getting started (BELL framework — the customer builds, evaluates and launches)docs.synthflow.ai · read August 19, 2026
- Docs: Custom pricing / reseller plans (Stripe reselling deprecated September 15, 2026; configurable subaccount plans, included minutes, concurrency caps, trials up to 200 minutes)docs.synthflow.ai · read August 19, 2026
- Docs index (call transfer TEL/SIP/dynamic, real-time booking, post-call SMS, in-call SMS/WhatsApp messaging, campaigns/batch calling, IVR handling, telephony and SIP integrations, Platform API)docs.synthflow.ai · read August 19, 2026
- Imprint (operating entity AgentFlow AI GmbH, Kurfürstendamm 15, 10719 Berlin; HRB 255004 B)docs.synthflow.ai · read August 19, 2026