No joke, I wasn't aware of how much value there is in MTG until a friend of mine put down $6000 investing in a bunch of cards. Then again, I don't know all that much about the game, but you can see that the market for cards on eBay is really active.
Some of my friends made good money playing the market: They bought during the summer drought and sold just after Christmas, when the kids had gotten money as presents.
