The market comes in four shapes
Self-serve apps run roughly $20 to $100 a month. You sign up, you configure it yourself, you test it yourself, and when it tells a caller something wrong at 9pm, you find out whenever you find out. Nobody at the company ever hears your calls.
Vertical software — built for one industry, usually clinics — runs a few hundred to about $1,500 a month. It is still software you largely operate yourself, aimed at one kind of business.
Human answering services bill by the minute, typically landing between roughly $250 and $700 a month for a moderately busy line. The person answering is juggling calls for dozens of companies at once, and a busy month is an expensive month by design.
Agency-built bots are one-off builds resold by marketing agencies, often around $350 a month or a one-time fee where you "own it" — which means you also own the maintenance, forever.
The question that actually matters
It isn't "how much per month." It's: who is responsible for what your phone says? With every option above, the answer is you. You do the setup, you catch the mistakes, you notice the misses.
A managed front desk flips that. Someone builds it to your business, tests it against real call scenarios before it ever goes live, and then a human reads every single conversation and fixes anything off, same day. That is a different product, and it is priced like one.
Why flat beats the meter
Per-minute billing means your best month — the month the phone rings off the hook — is your most expensive month. Read reviews of metered services and the bill surprise is the single most common complaint. A flat rate means growth costs you nothing extra, and you never hesitate to let the phone ring.