A&P's, are they like lawyers, they're on retainer as well as piece-work?
Dennis,
I WISH!!!!!!
No, it is power by the hour.
Annual Inspections are usually a fixed price. Then any thing found unairworthy and needs repair, that cost is per hour rate. Also, any additional maintenance or added mods are per hour rate.
Annuals are either you A&P/IA does the whole thing, or an Owner Assisted Annual. The owner assisted Annual will cost less for the Annual fee. Because you do all the grunt work.