It depends on the girl, of course regulars (and many new girls) would accept $80...but just because they accept it doesn't mean it's what most guys tip them. I'm guilty of tipping less for my regulars (but I see them practically every week so I think it's justified). If I'm seeing a new girl and I know she's above average in every way, then I tend to tip what I stated here.
Bottom line, if they are happy and you are happy, that's all that matters...