The platform advertises $0.07 a minute. You quote a client based on that, feel good about your margin, and then the first invoice is nearly double what you expected. The advertised rate is never your real cost. Here's the whole per-minute stack, the hidden fees that blow up the bill, and how to price so overages don't eat you alive.
The full stack, per minute
A voice minute isn't one cost — it's a stack of them:
- Platform / orchestration — the headline number (~$0.05–0.15/min depending on platform).
- LLM — the model doing the thinking. Often billed separately (BYOK) unless bundled.
- STT + TTS — speech-to-text in, text-to-speech out. Premium voices carry a surcharge.
- Telephony — the actual phone call transport, plus per-number fees.
Add them up and a "$0.07" platform can land at a true $0.12–0.35/min all-in. On some setups the BYOK provider stack alone adds $0.06–0.19/min on top of the advertised rate. That's the single most impactful hidden cost in the business.
The hidden fees that double the bill
- BYOK provider fees — voice, LLM, STT, telephony billed to you separately.
- Premium voice surcharges — the good-sounding voices cost more.
- Extra phone numbers — per-number monthly fees add up across clients.
- Outbound dialing markups — outbound often costs more per minute than inbound.
- White-label branding add-ons — $200–$500/mo on some platforms just to put your name on it.
- CRM integration fees and tiered support — the "enterprise" features you'll eventually need.
- Overages — the killer. A busy month blows past included minutes at the overage rate.
Why this wrecks margins
The math that looks like an 80% margin at the sticker rate can quietly become 50% — or negative on a high-volume account — once the real stack and overages are counted. Agencies that price on the advertised platform rate are pricing on a number they never actually pay.
How to price so it doesn't eat you
1. Price on your all-in cost, not the sticker. Run the true number: platform + LLM + STT/TTS + telephony. That's your floor.
2. Cap included minutes. Every plan gets a minute allowance ("up to 2,000 minutes/month included"). Past it, a fair overage rate kicks in. This is the single most important line item — it caps your downside on the account that suddenly triples its volume.
3. Prefer flat retainers with a fair-use ceiling over pure per-minute for SMB clients. It's easier to sell, easier to forecast, and the ceiling protects you.
4. Build a margin buffer. If your true cost is $0.15/min and you want a 70% margin at 2,000 minutes, don't price to the exact line — leave room for the premium voice the client will inevitably want.
5. Re-check quarterly. Provider prices move, and a client's volume grows. The account that was profitable in month one can quietly go underwater by month six.
The one-line takeaway
Your real cost is the whole stack, not the headline. Add it up, cap included minutes, price on the true number with a buffer, and never quote a client from the platform's marketing page. The margin you keep is the one you actually calculated — everyone else is guessing, and some of them are losing money on every call.