Like anything else, if you got in early and hooked even a few decent size players you are sitting back counting the cash these days.
Say you could have got even ten 5/10 players signed up under you affiliate ID and were keeping all the rake back.
I would say the majority of those pots get the max $3 rake so if between ten players they played 10000 hands a month your payment would be around $750 for only attracting 10 players.
1000 hands each a month is not really that much, especially if they multi-table, so thats actually a small number, I am sure several affiliates are making thousands a month from this.