As I've mentioned before, I don't just collect Joey Cora cards like I collect, say, Tony Gwynn or someone. I'm out to accrue as many copies of each issue as possible. I recently came across a batch of 24 Padres from the 1990 Donruss set on Listia. While I already had all of the cards, I still bid on the lot just to get another copy of that Joey. Sure, it's a little ridiculous and doesn't hold up to the sanity test if I think about it very much but I suppose I could say the same about collecting in general.
