I think the individual producers control the pricing of their materials as well as whether to participate in the weekly specials.  As I said, I don't remember the particulars, and I don't see the information on their site any more.  On their publishers page, though, they do mention that you get a 65 - 70% royalty (based on exclusivity) and that you must have at least one product for sale, you can't just have freebies.