I only quote jobs if someone asks for a quote. I much prefer to estimate jobs and work for time and material.
However if I'm doing a larger job for a contractor they are usually quoted jobs, but then again there isn't usually too many suprises.
The going rate for a plumber in my area is $75/hr so that's what I charge.
But yes this is not a cheap business to be in. Vehicle costs, gas costs, liability insurance, gas contracting insurance, payroll... the list goes on.
If I didn't charge what I charge I'd be out of business because when yo'ure in business EVERYTHING costs you money.