AKA The secondary market.
This one starts off ever so simple, how many cards in a pack? Eight is an average size, but where's no guarantee of getting one of the better rare cards. Then you have MTG's 15 cards with a guaranteed one rare and three uncommons. Yu-Gi-Oh's variable rarity system is pretty interesting, but how much of it is there to fuel the secondary market? You could argue both do that in their own way, but I can't help but feel that YGO is far more blatant about it.