mars1985 Yeah, its around $5, but the cranberry plugins are more than worth it. I've not field tested chartboost so I can't talk about it financially (though enough people have done) but as for functionality it works fine.
I should also note that I've only ever used their video ads so I can't comment on banner ads.
The only one I can't recommend is admob, you really might as well not bother if the goal is profit. (Field tested with GATE)