Most AI voice is sold by the minute, on top of a telephone carrier that also bills by the minute. SARAH Voice Link is a flat $300 a month per AI extension with unlimited minutes. Here is the arithmetic, using public prices read on 24 September 2026.
A voice agent needs a telephone path and an AI path. The question is whether either of them runs a meter.
A cloud carrier bills for each minute on the line, from $0.0085 a minute to receive and $0.0140 a minute to call out on Twilio [1]. The AI platform then bills its own minutes: $0.07 to $0.31 on Retell [4], $0.05 of hosting plus speech, model and voice on Vapi [5], $0.08 on ElevenLabs Agents [6] and on xAI's Voice API [7]. Every extra minute of conversation is an extra line on the invoice.
Voice Link is a complete telephone system with SARAH on it: $300 a month per AI extension, unlimited minutes and no per-minute charge to receive a call [8]. Connect the phone system you already run over SIP and SARAH becomes an extension on it; human and AI extensions share one dial plan and transfer calls between them [8].
Public per-minute prices multiplied by the same workload. The single-line column assumes 10,560 minutes a month; the twelve-line column assumes twelve lines doing the same, 126,720 minutes.
| Service | Published price | 1 line a month | 12 lines a month |
|---|---|---|---|
| Twilio, receive a call on a local number [1] Telephone carriage only. No AI. | $0.0085 a minute | $89.76 | $1,077.12 |
| Twilio, make a call [1] Telephone carriage only. No AI. | $0.0140 a minute | $147.84 | $1,774.08 |
| Twilio Elastic SIP Trunking, inbound on a local number [2] Carriage only. No AI. | $0.0034 a minute | $35.90 | $430.85 |
| Retell AI voice agent, all in [4] Retell's published all-in range for AI voice agents. | $0.07 to $0.31 a minute | $739.20 to $3,273.60 | $8,870.40 to $39,283.20 |
| Vapi voice agent, calculator default [5] Vapi hosting $0.05 a minute, plus speech, model and voice passed through at cost. | $82 to $129 per 1,000 minutes | $865.92 to $1,362.24 | $10,391.04 to $16,346.88 |
| ElevenLabs Agents, additional minutes [6] Their published rate for minutes beyond a plan's allowance. | $0.08 a minute | $844.80 | $10,137.60 |
| xAI Voice API, agent [7] Their published agent rate. | $0.08 a minute | $844.80 | $10,137.60 |
| SARAH Voice Link [8] One AI channel: one conversation at a time, unlimited minutes, no per-minute charge to receive a call. | $300 a month per AI extension | $300.00 | $3,600.00 (12 channels) |
Keep a flat-rate business phone plan for your people, and put SARAH on the same dial plan.
RingCentral RingEX lists Core at $20 a user a month billed annually or $30 billed monthly, and Advanced at $25 billed annually or $35 billed monthly, with unlimited calls within the US and Canada [3]. Prices on that page vary with the number of users.
A public number can point straight at a SARAH extension as a SIP URI. There is no SIP trunk to rent for that path and, in markets such as the United States where receiving calls is billed, no per-call cost to answer [8].
The language model, speech recognition and speech synthesis on the voice path are hosted by us, on GPUs we operate. There is no per-token invoice to a public model while your customer is speaking, so there is nothing to pass on by the minute. The telephone system underneath, the PBX, the SIP gateway and the WebRTC gateway, is our own [8].
Third-party prices were read from the vendors' public pages on 24 September 2026. Our own prices are from our live pages.
A thirty-minute call is enough to size your extensions and see what your current meter is costing you.