i agree with merin,
whoever asks is the one that pays.
when you ask somebody to accompany you for the evening, it's an invite and you are supposed to treat them.
usually, at least in my experience, the man is the one to ask out, therefore, he pays for the evening. but that's just me.
i recipricate with my fiance. mostly, he pays when we go out (we never go anywhere big or expensive though), but I treat him to dinner and drinks too.
traditionally speaking, if the man pursues the dating, then he should be treating her for the first 3 dates, then they can recipricate. same for a relationship.
and i know that i said this, it will become very controversal amongst men complaining it isn't fair. please don't attack me !