I think if its your wife its really about Love and affection first then fun
whereareas if you pay someone its not about love or affection but rather carnal pleasure for ones own sake, thus one negates the humanity of the other and uses them as a use object for pleasure to be discarded
if you ever see a young prostitiute in a movie who is doing it cus she has no choice and is sad and being eaten away you will know what I saw ( I met a real girl in this predicatamant)