It depends. Modern day base (common) cards a worth little to nothing, but are still fun to collect; modern rookies have a broad range and you can find how much they are going for on eBay. Most people who collect modern day cards (like me) go for the hits (autograph, autographed jersey cards, and jersey/patch cards). Again look for how much they are going for on eBay.
Older, or vintage cards, are only worth what a collector will pay for them. I personally do not collect the old ones.
Hope this helps!
Remember, all cards are based on their conditions, and if they are in terrible shape, they won't be worth much, and vice-versa.
Chat with our AI personalities