I never did like being charged for work that people didn't do, so I only charge for what I do.....If I don't fix it, you don't pay. Instead of charging as if it took longer, When I fix it sooner than planned, you save money.
I also have fewer expenses that the other guys. Examples......
1. I own all my tools, so I don't have to make that payment to the tool truck every week.
2. I do some mobile repairs as well as owning the place where I work, so I don't have to pay rental on an expensive shop that may not always be used.
3. I don't have to keep 6 guys busy, and don't have to write payroll checks for 6 guys every
week.
4. My work uniforms are bought used, and
I don't pay a lot for the shirts that I wear.
5. Since I don't sell parts, make your best deal on parts, then see me for a quality installation. If they quote you the "installed price", ask them how much less it will cost you if they don't install it.
There may be other reasons.....but I think you are
getting the idea...

-Bob