It depends on the girl and the customer. For a regular you might not be charged but you might give a tip. If the girl wants a little extra she will ask, so don't be shy. Those who charge will usually be $20 to $50.

Most girls do know what greek is, at least the ones who offer it do. Barbie does. Some of the ones with not so great English might not, the few I'm not sure if they offer it, if I ask, I usually have to say something like 'fuck arse' or point to my bum and say 'me fuck you bum' or similar LOL. Eventually they work out what you are asking (and usually are shocked and say 'oh no no no!!')