I used to work for an agency where one of their lines of practice was affiliate marketing (traditional CJ/Linkshare model for big brand-name clients), and also had a media team that not only worked with banner buys/email publishers, but also ran those offers in CPA networks. There's even a case where the agency for a large brand-name client contracted this other agency to put offers out in CPA networks, so the real chain is Advertiser -> Main Agency -> Second Agency -> CPA network -> (perhaps another CPA network) -> Publisher. The payout on that offer that I get straight from the 2nd agency is almost double what I see the offer for in most CPA networks, and the agency I get it from is already taking a 20% fee from what they're paid per lead.