It's too bad you can't make the guy mow your lawn or something to earn the remainder of his "day"! I do not expect to be charged for 8 hours when the man only took 5 on my site. Those part days and travel time should be part of their labor rate.
Sounds good. I doubt
@Calentarse was provided with this kind of quote and he/she was smart enough to figure out that the markup on parts was not 15%.
Is there maybe some reason, like taxes, that an installer would want to hide profit in parts markup instead of labor?
In the end, all the homeowner can do it compare total bids. It shouldn't matter much whether the parts markup is 200% and the labor is cheap or the labor is expensive and the parts are at cost. When this can bite the homeowner is when there is an overrun in either parts or labor and the installer chooses to charge for it. Then the unreasonable markup can be the method for the installer to screw the homeowner.
Labor rate is not salary. Most places have around a 3x multiplier.