- Your COGS scales with talk time — per-minute pricing ties your cost to how much your client's phone rings, the one variable you don't control.
- Busy months eat the margin you quoted — a chatty caller base or a good season means you either pad the retail price or absorb the variance yourself.
- You're also the engineering team — prompt plumbing, a telephony stack, edge cases, and the 2am page when a call flow breaks. That burden never shows up on the pricing page.
Fixed retail on top of a variable cost is a bet, not a margin.