Ironic timing of this post. Yesterday I had a customer who is a collector of many things. He happens to own 2 Michael Jordan rookie cards. One is signed. Google the value of these things.
Possibly worth couple of grand or a lot more depending on condition as long as they're not reprints. Check ebay completed auctions.
Those high value cards are like stamps and coins, they need to be professionally graded to know what they're worth.