I can charge MORE because I am fast, but because I am fast the customer pays less than they would have to someone else. As I tell them, "If you want a cheaper plumber, I can give you some names, but you will pay more to them". It is always better to be "fast" or "super fast" than "half fast".
Awww, HJ, you beat me to the half-fast thing
I am definitely not a pro plumber, but I am a pro crastinator