Retell vs Synthflow
Two AI voice agent platforms you buy in very different ways. Retell is a self-serve rate card. Synthflow is a custom-quoted enterprise plan.
Choose Retell when you want to test call quality for a few hundred dollars before you commit. Choose Synthflow when your rollout is big enough for a five-figure yearly contract. Its team scopes phone setup, security review and launch support around your volume.
The short answer
- Retell publishes a pay-as-you-go rate card. You pay a voice fee, plus separate line items for the language model, text-to-speech and phone lines.
- Synthflow's pricing page lists one Enterprise plan, from around $30,000 a year. It's scoped to call volume, concurrent calls and integrations, not a flat rate.
- Retell fits a developer or agency that wants to try it today with a card and a small budget. Synthflow fits a firm ready for a scoped, sales-led 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 by model), phone lines (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. Price depends on volume, concurrent calls, phone setup and security review |
| Positioning | Rate card for developers, with each cost listed | Enterprise platform built on its own phone network and security 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 tier below Enterprise. We show no lower price because none is public.
What each platform does well
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
- Separate line items (LLM, TTS, phone) mean the real cost per minute varies a lot by setup
- No published enterprise commitments, such as the phone network promise Synthflow markets
Synthflow
- Markets its own phone network, not only third-party carriers, and pitches that as more reliable
- Enterprise plan bundles security review, onboarding and launch support into one scoped deal
- No public pricing below Enterprise. You can't test it cheaply before a sales call
- A $30,000-a-year starting point rules out small teams and early testing
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 fits. You can build an agent, run test calls and see the real cost before you sign anything. That matters, because a voice platform's headline rate is rarely the full bill. Retell's $0.055/min voice fee is only the floor. The language model, text-to-speech and phone lines are billed on top.
Maybe you already know your size: roughly how many calls at once, and how much volume each month. Then Synthflow's enterprise pricing makes more sense. Its plan folds phone setup, security review, and launch support into one scoped deal. That suits a firm doing a formal rollout. It suits a team still deciding on AI voice agents less well.
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?
- You could run a small pilot on each. Neither one locks you in. Most teams don't, though, because the two sit at very different price points. You can test Retell's pay-as-you-go plan for the cost of a few hundred minutes. Synthflow's public pricing starts near a five-figure yearly deal. So most buyers test, then pick one, instead of running both.
- How do you switch from Synthflow to Retell, or the other way?
- Most of the work is rebuilding the agent, not moving data. Call scripts, prompts and voice choices belong to each platform, so you rebuild them on the new one. Phone numbers can often move with you. That works if you bought them through a carrier that allows porting, not the vendor's own phone stack. If keeping your numbers matters, check this before you commit.
- Why is Synthflow's pricing so different from Retell's?
- Retell publishes a pay-as-you-go rate card. It's built for a developer or agency to sign up and start testing right away. Synthflow's pricing page shows one Enterprise plan, starting around $30,000 a year. The price is scoped to call volume, concurrent calls, phone setup and security review. That's a sales-led model for larger rollouts, not a self-serve trial.
- Do I need a CRM behind either platform?
- Yes. Retell and Synthflow both build and run the voice agent: the part of the call that listens, decides and speaks. Neither tracks what happens after the call. Was the lead booked? What was the outcome? What's next? That record lives somewhere else, whichever platform runs the call.