I'm pretty certain that I've got somewhere between 5,000 and 10,000 cards. If it's more than 10,000, it isn't by much. My father, on the other hand, has well in excess of 30,000 cards. At any one time, he has around fifty playable decks (3,000 cards) that occupy two drawers in the case he has devoted to Magic cards. The other seven drawers are also filled with cards. He's got a couple of 1,000 card boxes (which actually hold closer to 1,300 Magic cards) full, and there are always several stacks of 500+ cards sitting on top of the case.