Anyone hoping to recover the purchase price of a DU dinner gun is going to be sadly disappointed in most cases.
I'm a DU member, attend at least a couple of events each year, and am under no illusions what their guns and the rest of their merchandise are really worth.
Someone who goes to a DU dinner dreaming of a great score on a fancy gun is an idiot who deserves whatever financial beating he gets. You are there to support a conservation organization that does good work preserving the wetlands. If that doesn't appeal to you then stay at home.