Simply, a chap spending an evening with a whore could be settled rather reasonably for a little cash,
whereas a similarly happy ending with his wife may run into real money. So he may consider that he has made a decent saving.
This is the thing, really. It's considered fine for a man to lavish a lady with expensive gifts and restaurants and holidays to bribe his way into her knickers, but not when the arrangement is explicit from the start. :shrug:
And the other thing is that it has been said that in many cases the man is not paying the professional for sex, but paying for her to go away afterwards.
Well, your first point describes my courtship and subsequent marriage, and that arrangement was certainly fairly explicit from the start (and apparently still is, if 'er indoors' Amex bill is anything to go by), if only because we didn't enjoy a shared spoken language we could otherwise communicate in.
Secondly, perhaps there's a crucial difference between "paying for her to go away afterwards" and merely paying for the right to not be expected to stick around afterwards, as it may be understood from the beginning? Had my wife and I chosen not to continue the ̶f̶a̶r̶c̶e̶ relationship, what harm would've been done?
Actual real, cash money is so readily available nowadays that how one makes it doesn't really carry any stigma at all anymore, literally however it is you do it. Surely if my children can accept that their birthday parties and Louis Vuitton jeans and iphones are paid for by my warmongering, would it really concern them if it was through whoremongering or growing pot instead? It's just business, innit. Work.
Similarly, does even a decent, responsible adult care too much about any funny looks she may get from her family and friends as they learn where the money for her new car came from or how her munificent expenses get paid, even if it's obviously from a succession of wealthy, generous "gentleman visitors"?
It's the working and making money that overcomes any ethical objections now. And that goes for M's pariah-ed meat producers as it does for even the Gambino family and professional athletes and drug-addled rock stars. It wasn't long ago that footballers were considered amongst life's losers and ne'er do wells, was it. And many middle-class types who actually finished school still can't quite get over it; all that money for kicking a ball about, indeed. Even moreso now that age and apparent talent or success is not a barrier to earning a fortune out of the game. Frankly, whatever it is people do to make shėtloads of the stuff, everyone else simply wishes they had thought of doing it too.