I spent a good portion of last summer going through all my baseball, football, hockey, basketball, and soccer cards. I priced them all on www.beckett.com
I was really surprised at how much the value of some of them decreased. I think my most expensive card now is some UD Ionix Insert card of Derek Jeter valued at $80.
A few years ago when I stopped I had a UD MVP Game Used Souvenir card of Ken Griffey Jr. with a piece of his bat used in a game in the card valued at $200. Also, I had a early 2000 Topps Commemorative autographed Frank Robinson card that was around $200 if not more.
Now the Griffey is like $40 and the Robinson is $50. Kinda sucks, but honestly collecting cards for me was never really about how much they were worth because I will probably never sell them unless I am seriously in financial trouble.