The male point of view seems to be that it is neither cheating if you are being paid or paying for it. I can't say I'm surprised about this but it does make me wonder about how many of them actually do it.
My opinion is that if you are with anyone besides your partner, no matter the circumstance, it is cheating. And I've never understood the whole 'open-relationship' thing. If you like someone enough to want to be in a relationship with them why would you want to be with anyone else?