Few things provide a better return on investment than sports cards. Baseball and hockey cards that are often bought for a buck or two can end up being worth millions of dollars if a player has a great career or gets inducted into the Hall of Fame. And when players reach legendary status in their respective sport, the value of a collectible trading card can really skyrocket. This is true of star athletes still playing today. Hockey player Sidney Crosby’s rookie card, issued by card company Upper Deck in 2005, originally sold for less than $2, but is selling today for $400. That’s a huge profit for anyone who has the card lying around in an old shoe box. So with value for money in mind, here are 10 of the most valuable sports cards ever sold.