I don't own one of these yet, but so far prices have been reasonable from sold listings on ebay. I think they are averaging under $30. The majority of cards I've seen use a signed Hall of Fame plaque postcards. However I've found one listing that looks like a signed index card. All cards are encased and are limited to just 46 examples.
You get one card per box, and right now boxes are going for about $50 online.
If I find any different examples I'll post them here.