HUGE difference depending on what you mean by your question. Are you asking about someone who sells direct advertising on thier site, or someone who shows banner network ads like Tribalfusuion, or how much CPM they make with Adsense.
If you are asking how much money people make with affiliate programs if they translated that to CPM (which is not how affiliate programs pay.) That would vary wildly depending on how well the affiliate program converts and how targeted the affiliate's traffic was.
Above are all different ways to make money but the amounts would vary wildly. Also the type of site you have plays a huge part. A celebrity gossip site or humor site has notoriously low conversion rates for example.
The following thread answers your question pretty well (although I think it's talking about selling direct advertising on your site, which may not be what you were referring to.) The right answer is "it depends" but this will give you some ranges.
Average CPM today?
Note it's from 2005 so the numbers may be a little different but the comments are still valid.
TO be sure you understand CPM - CPM stands for "cost per thousand impressions" so for example having your ad appear 500,000 times on a site at a CPM rate of $4 would cost $2,000 (500,000 impressions x $4 / 1000).
Maybe that's more detail than you wanted or not what you wanted to hear.
But if you were just looking for an answer to how much the answer is it depends. Above will just give you some ideas.