As far as why some sell for more than others - for some cards, there are sometimes more rare variations of them like a Griffey Jr Tiffany's card in a set that also has a simple base card. They look similar, but are slightly different.

Some that sell for high are also because they might be graded by companies like PSA, SGC, etc.

For cards from the 80s and 90s, they are considered part of the "junk wax era" where cards were so over-produced that the value was driven down due to their population. There can still be value, but it is all about condition and the player from that era.

One other caveat to the sold ebay listings you may have seen that were crazy high could have been a seller trying to drive up the sale value of his card by either him bidding up the price of his own auction, or having friends do it for him.

Feel free to boardmail me any other questions or value of specific cards.