"I always thought that it was kind of silly that a baseball card could be worth so much money"

Matthew Modine's quote suggests that he discovers it odd that a baseball card can be worth a big amount of money. He indicates that he does not understand why a baseball card, which is basically a piece of cardboard, can be worth a lot. This might be since he does not comprehend the worth of the card, or the sentimental value it holds for some individuals. It might also be since he does not understand the rarity of the card, or the fact that it is a collectible item. Whatever the reason, it is clear that Matthew Modine finds it strange that a baseball card can be worth a lot money.