If you are quoted a price per hour, and a job is finished in less than an hour, would you expect to pay the relevant proportion of that rate or pay for an hour? And, what if a job takes say 1.25 hours? Would you pay the rate x 1.25 or pay for 2 hours? This is with the assumption you haven't been told there is a minimum charge. I don't like cross examining someone, particularly if I'm hoping to get them to do a job for me.