Considering how loose morally the western world has become... why not? Infidelity rates are soaring anyway. Women say "well he was ignoring me... so I was driven into the arms of another man" as a pathetic (but socially acceptable) attempt to escape her conscious. Married men just as much... but you don't see us going around saying "it was okay because my wife ignored me". Men are automatically labeled scumbags for that. Might as well make some mulah $$$.
It's not so much the idea of my wife sleeping with someone else, and it's not even about her doing it for money either, but I think if only $1,000,000 is enough to sway her decision in this matter, then I would be disappointed in myself for not making enough money.