Even in this world, there are ethics: guy pays up front for services not yet rendered, lady assumes guy won't hurt or take advantage of her, etc. Obviously, these are the ideal and not necessarily the way it turns out, but more often than not I believe it is the case that a transaction happens the way it should.
So, how can it be justified, ethically speaking, that a gentleman does not get the time that he paid for just because he finishes prematurely?
By that logic, shouldn't he get some money in return? If, as many of you claim, the donation is for time and time only, should he not be refunded for the time not spent?