Before hands made it too painful to sew I loved designing & making clothes, but never liked doing alterations 'n such. Over thirty years ago I charged $7.50 to hem dress or slacks of regular width...more for fuller ones.
A call to a local alteration shop or dry cleaners will get you some answers, I'll bet.

Suzi

Check local places, for sure. Don't try to undercut the dry cleaners in your area: you'll give your customers more time and attention. If you try to be the cheapest in town, you'll probably live to regret it. You are performing skilled labor.
to compare: how much does it cost to have your hair cut, and how long does that take? Remember that you have overhead, even in your home. It is quite common to find out after expenses, you keep about half of what you charge.

Ihave set prices for a few things that stay predictable,Like pant hems. If someone has multiple garments, I charge by the hour,plus materials.