I got them at a hobby shop in bulk
Hi Schauer-- I'm thinking that the fact that you bought them in bulk at a hobby shop is part of the answer. It may have been a collector putting some duplicates together for the hobby shop, and I'm guessing for $5.00 or less.
They mostly seem like they're in good condition, which is amazing, but you have all common stamps in your image.
Good luck, and hope you renew your collecting interest!!