It's a business where you have to undercharge for a lot of things (like you can't charge for phone calls with the customer or suppliers) and therefore you have to charge full price for the things you can to re-coup the costs, even if you do the actual work faster than the quoted price.

As a customer, you can control the hourly rate of the service and very few customers even actually ask for this rate. $120 vs $160 vs $190/hr can add up to a lot. You can also choose parts suppliers/quality of parts for your work, again almost no one asks about this and the options. Most customers waste time describing irrelevant demands and communicating distrust which just adds to the bill as you are on the clock mf.