Vapi

Vapi sells the middle of a voice pipeline to engineering teams who already know which transcriber and model they want. It handles turn-taking, interruption detection and telephony routing; you bring the prompt, the tools and the provider keys.

Billing has two layers the vendor never merges. Hosting is $0.05 a minute for calls and $0.005 a message for SMS and chat, drawn from prepaid credits topped up in the dashboard. Speech-to-text, the model and the voice bill separately at provider cost, and drop to $0 on your own API key. Ten concurrent call lines are included, then $10 a line a month. Minutes are wall clock, from call start to call end.

On the self-serve Build plan there is no SSO, no RBAC and no uptime SLA, and call history lasts 14 days (chat, 30), so anything you want later must be pulled through the API or written to your own bucket first. HIPAA mode costs $2,000 a month, Zero Data Retention another $1,000, and the two cannot both be on. An EU region exists but is frozen to new self-serve accounts until 2027.

Retell AI prices every model per minute instead of passing it through, so one page costs a call. Bland AI meters minutes the same way. PolyAI publishes no rate at all, leaving these two the AI voice agents you can budget before a sales call. Lorikeet bills per resolved ticket, so a failed call is free there and full price here.