i always tried to talk them out of a quote by letting them know that if it's quoted that's the price. if we come in under on the labor good for us if we come in over good for you and because of that we're going to quote higher than what it might take on average to do the job to cover minor deviations like "stripped bolts" (or more likely lost bolt or that wire terminal you broke). bottom line, you want a quote you are probably gonna pay more than with no quote. i always found that if you tell it like it is up front there are no hard feelings after.