Well, the thing with it is that there's no information about how one can become a merchant. If no one can become a merchant besides SmartMonsters and a couple of other services, no one can compete.
As a sidenote, the +75 packs for buying 500 gives a discount of a bit less than 15%. They could get packs for about $1.30 this way, which is a 35% discount.
Sorry I didn't listen to you. I tend to like facts and figures. I am pretty sure though, that the merchant terms have been changed now, due to this misunderstanding with a merchant that stands to show that this could happen again.