Most comparisons of these two are about no-code versus developer tooling. That framing is fine and it skips the only question with a number attached.
Synthflow publishes one figure, and it is annual
Synthflow's pricing page publishes no monthly tier and no per-minute rate. It publishes a single number: enterprise contracts start at $30,000 a year, scoped around call volume, concurrency, telephony setup, integrations and security.
There is no self-serve path. The self-serve tiers with included minutes that ranking reviews still quote are not on the page, and this directory recorded that correction after a re-check: we had Synthflow at $29 a month and it was wrong by three orders of magnitude.
Vapi publishes a rate that excludes four things
Vapi advertises $0.05 a minute with no platform fee, self-serve, no sales call. The comparison table on its own pricing page is headed Excludes Model Provider Costs.
Speech recognition, the language model and synthesis are billed at cost on top, and telephony sits outside the platform entirely. This directory computes the all-in at $0.0965 a minute, and Vapi's own calculator reaches $0.1103 on its default inputs.
The crossover
A $30,000 annual contract is $2,500 a month. Divide that by Vapi's computed all-in and you get the volume at which the contract stops being the more expensive option.
| Basis | Rate | Minutes to reach $2,500/mo |
|---|---|---|
| Vapi computed all-in | $0.0965/min | ~25,900 |
| Vapi advertised sticker | $0.05/min | ~50,000 |
| Bare component floor | $0.0465/min | ~53,800 |
So the honest answer is a range rather than a point, and it depends which Vapi number you believe. On the all-in figure the contract breaks even around 25,900 minutes a month, which is roughly 6,500 four-minute calls.
Below that, the Synthflow contract costs more than every component it orchestrates. Well below it, the gap is enormous: a team running 2,000 minutes a month would pay about $193 on Vapi's computed rate against $2,500 contracted.
What the contract buys that the meter does not
Three things, and they are real.
A ceiling. A metered bill has no upper bound, and a runaway agent or a spike in call volume lands entirely on you. An annual contract is a known number you can budget against, which is worth more to a finance team than the arithmetic suggests.
Scoped integrations and telephony setup, which on the metered route are your engineering time. And security review, which for anyone selling into a regulated buyer is not optional and is slow to assemble yourself.
Which one you are
If you are evaluating these two against each other and you do not already know your monthly minutes, that is the finding. Synthflow's entry point is priced for an organisation that has measured its call volume and found it large.
For anybody else, the metered platform is not a cheaper version of the same purchase. It is the only one of the two you can start on this afternoon and abandon in a fortnight, which at the evaluation stage is worth more than any per-minute rate.