Retell AI vs Synthflow — Pricing, Plans, and Verified Costs (2026)
Retell AI starts at Free. Synthflow starts at $29/mo. Retell AI is $29/mo cheaper on the entry tier than Synthflow.
How pricing works
These two tools don't price the same way, so the headline numbers below aren't directly comparable until you plug in your own volume.
- Retell AI (Per Usage) — Retell AI bills purely on usage — PAYG. There is no fixed per-seat fee, so the monthly cost depends entirely on how much you consume.
- Synthflow (Hybrid) — Synthflow is hybrid: a fixed subscription from $29/mo plus metered usage on top (Starter). Your real bill moves with volume, not seat count.
Per-minute, per-credit and per-token rates exclude any downstream model, speech or telephony costs unless the vendor states otherwise.
AI voice agent platform. PAYG at $0.07+/min base ($10 free credits, 20 free concurrent calls); real all-in cost $0.13–0.31/min. Enterprise drops to $0.05+/min base rate. Supports GPT-5.x variants and Claude 4.5/4.6 Sonnet; Fast Tier LLM adds 1.5–2× charge for lower latency. Direct competitor to Vapi and Bland AI.
No-code AI voice agent builder with tiered subscriptions + per-minute overages. Starter $29 (50 min), Pro $99 (200 min), Growth $449 (1000 min), Agency $899 (2000 min), Enterprise custom (10K+ min). White-label option runs ~$2,000/mo. Voice engine alone ~$0.09/min; all-in $0.15–0.37/min with LLM + telephony.
All plans compared
| Tier role | Plan | Retell AI monthly | Retell AI annual | Synthflow monthly | Synthflow annual |
|---|---|---|---|---|---|
| Free / starter | PAYG / — | Free | Free | — | — |
| Entry paid | — / Starter | — | — | $29 | $29 |
| Mid tier 1 | — / Pro | — | — | $99 | $99 |
| Mid tier 2 | — / Growth | — | — | $449 | $449 |
| Pro / power | — / Agency | — | — | $899 | $899 |
| Enterprise | Enterprise | Custom | Custom | Custom | Custom |
Tier names differ across vendors. Rows are aligned by tier role, not name. Full tier structures on each tool's page.
What each is best for
Retell AI is worth it if… developers who want a slightly more opinionated voice stack than Vapi — bundled defaults that ship faster, with paid unlocks for premium voices and Fast Tier LLM latency. Free credits make prototyping frictionless.
Synthflow is worth it if… small businesses and agencies that want no-code AI voice agents without touching a developer platform like Vapi or Retell. Starter ($29) makes prototyping cheap.
Bottom line: Choose based on how you want to pay — Retell AI is per usage, Synthflow is hybrid.
Choose Retell AI over Synthflow if…
Choose Retell AI if…
- You want bundled defaults that ship faster than assembling components yourself.
- You're building voice agents where developer experience and UI matter more than stack flexibility.
- You want premium voices and low-latency model tiers behind a simple paid unlock.
Choose Synthflow if…
- You're fine with a base subscription plus metered usage on top (from $29/mo).
- You match the profile Synthflow is built for: small businesses and agencies that want no-code AI voice agents without touching a developer platform like Vapi or Retell.
- You need a general-purpose voice agents & speech/audio option rather than a vertical-specific one.
Feature comparison
| AI Voice Agents | Retell AI | Synthflow |
|---|---|---|
| Bring-your-own LLM | Partial | |
| Bring-your-own voice | ||
| Multilingual (5+ languages) | ||
| Inbound + outbound | ||
| Human transfer | ||
| HIPAA | ||
| SOC 2 | ||
| Self-serve signup |
Feature parity verified against vendor pricing and docs pages on September 10, 2026. Missing a feature? Tell us — we'll fact-check and update.
At a glance
| Retell AI | Synthflow | |
|---|---|---|
| Free plan | Yes | No |
| Entry price | Free | $29/mo |
| Enterprise available | Yes | Yes |
| Pricing model | Per Usage | Hybrid |
| Last verified | September 10, 2026 | September 10, 2026 |
| Full pricing | View full pricing | View full pricing |
Pricing last verified September 10, 2026. Tracked daily.