Florida
to determine what's really fair compensation for the provider, one would have to know the "true" reason the gentleman is opting out - and because of the awkwardness of the situation, most gents are not completely candid on this point IMHO. not that i blame them...i absolutely don't!...because no matter what a man says when turning a provider away, he runs the risk of provoking a confrontation of some sort. women, after all, are emotional creatures! so, i do believe it's best he make a vague excuse to avoid as many bad feelings as possible, and make his exit as quickly as possible. there's no sense in making a bad situation worse!
having said that - and having yet to answer the question, LOL - i would say that the gentleman should take into consideration whether "fault" exists. if a provider clearly was disingenuous and misleading in her representation of herself, shame on her, and the amount should be no more than a token amount, maybe $20. trust me, if she was that badly in the wrong that a guy cannot go through with a date, she knows it! if, however, the reason is something less tangible and/or beyond her control (for example, the gentleman is not comfortable with the incall or he is simply NOT attracted although she clearly IS the lady in the pics), she should be compensated more in line with the fact that she did in fact set aside the time and made an effort on the gentleman's behalf...perhaps 25-50 percent of her rate, depending on the reason.
edited to add: please note, i am answering this as a hypothetical question. 
-- Modified on 6/22/2012 7:24:00 AM
So true! My jaw still hurts when it the floor the first time you opened the door. You also do a great job posting new pics all of the time. Only good suprises with you. 