Retell vs Synthflow
Two AI voice agent platforms with very different buying motions: one is a self-serve, pay-per-component rate card, the other a custom-quoted enterprise plan.
Choose Retell when you want to test call quality yourself for a few hundred dollars before committing to anything. Choose Synthflow when the deployment is large enough to justify a five-figure annual contract and you want a vendor that scopes telephony, security review and launch support around your specific volume.
The short answer
- Retell publishes a self-serve, pay-as-you-go rate card: a voice-infrastructure fee plus separate, itemized costs for the language model, text-to-speech and telephony.
- Synthflow's public pricing page lists a single Enterprise plan starting around $30,000 a year, scoped to call volume, concurrency and integration needs rather than a flat published rate.
- Retell fits a developer or agency that wants to try the platform today with a card and a small budget; Synthflow fits an organization ready for a scoped, sales-assisted rollout.
- Neither platform is a CRM. Both hand off call outcomes, bookings and dispositions to whatever system tracks the pipeline afterward.
Retell vs Synthflow at a glance
| Dimension | Retell | Synthflow |
|---|---|---|
| Published pricing | Pay-as-you-go, from $0 to start with $10 in credits | Enterprise plan starting around $30,000/year, custom-scoped |
| Voice infrastructure rate | $0.055/min | Not published; part of the custom quote |
| What's itemized separately | Text-to-speech (from $0.015/min), LLM ($0.003–$0.16/min depending on model), telephony (from $0.015/min) | Rolled into the custom quote; not broken out publicly |
| Free concurrency included | 20 concurrent calls on pay-as-you-go | Not published; scoped per contract |
| Buying motion | Self-serve signup, no sales call required to start | Contact sales; final price depends on volume, concurrency, telephony setup and security review |
| Positioning | Developer-facing rate card, itemized cost transparency | Enterprise-ready platform built around its own telephony infrastructure and compliance posture |
| Best-fit use case | A team that wants to test call quality and cost before committing | An organization with enough call volume to justify a scoped enterprise contract |
Figures checked on vendor pricing pages, September 2026 (retellai.com/pricing, synthflow.ai/pricing). Synthflow's site lists no published tier below Enterprise; no lower-tier price is invented here because none is publicly stated.
Where each platform holds up, and where it doesn't
Retell
- Public, itemized rate card lets you estimate real cost before talking to anyone
- Self-serve signup with 20 free concurrent calls to test with
- The itemized components (LLM, TTS, telephony) mean the real per-minute cost varies a lot by configuration, not one flat number
- No published enterprise-scale commitments like a telephony-infrastructure guarantee the way Synthflow markets
Synthflow
- Markets its own telephony infrastructure rather than relying entirely on third-party carriers, which it positions as a reliability advantage
- Enterprise plan bundles security review, onboarding and launch support into one scoped engagement
- No public pricing below the Enterprise tier, so there is no way to test the platform cheaply before a sales conversation
- A committed $30,000-a-year starting point rules out small teams and early-stage testing entirely
How to choose
Start with how much you're ready to commit before you've heard a single call. If the answer is "not much yet," Retell's pay-as-you-go plan lets you build an agent, run test calls and see the real itemized cost, all before signing anything. That matters because a voice platform's headline rate rarely reflects the full bill; Retell's own $0.055/min voice-infrastructure fee is just the floor, with the language model, text-to-speech and telephony billed as separate line items on top.
If the deployment is already sized, meaning you know roughly how many concurrent calls and how much monthly volume you're running, Synthflow's enterprise-only pricing makes more sense. Its plan folds telephony setup, security review, and launch support into one scoped engagement, which suits an organization doing a formal rollout more than a team still deciding whether AI voice agents are worth adopting.
Either way, plan for something behind the call to catch the result. Neither Retell nor Synthflow tracks the deal, the follow-up task, or the disposition after the agent hangs up. That's a separate system, and it needs to exist before either platform goes live.
Questions
- Can you use both Retell and Synthflow?
- There is no technical reason you couldn't run a small pilot on each, since neither locks a business into exclusivity. In practice, most teams don't, because the two sit at different price points and different levels of commitment: Retell's pay-as-you-go plan can be tested for the cost of a few hundred minutes, while Synthflow's public pricing starts near a five-figure annual commitment, which pushes most buyers to pick one after an initial evaluation rather than run both in parallel.
- How do you switch from Synthflow to Retell, or the other way?
- The switching cost is mostly in re-recording or re-configuring the agent, not moving data. Call scripts, prompts and voice choices are platform-specific and have to be rebuilt on the new platform. Phone numbers can usually be ported if they were bought through a portable carrier rather than tied to the vendor's own telephony stack, so check that before committing to either platform if number continuity matters.
- Why is Synthflow's pricing so different from Retell's?
- Retell publishes a pay-as-you-go rate card because it is built for a self-serve developer or agency to sign up and start testing immediately. Synthflow's public pricing page shows a single Enterprise plan starting around $30,000 a year, scoped around call volume, concurrency, telephony setup and security review, which is a sales-assisted model aimed at larger deployments rather than a self-serve trial.
- Do I need a CRM behind either platform?
- Yes. Both Retell and Synthflow build and run the voice agent itself, the part of the call that listens, decides and speaks. Neither is a system of record that tracks what happened after the call, whether the lead was booked, what the disposition was, and what happens next. That has to live somewhere else, whichever platform runs the call.