The same thing happened with baseball cards......When I use to collect baseball cards they were high dollar simply because there were only a few in the market (Topps, Donruss, Score, and a few others). Now the market is flooded and prices are horrible and have been horrible for years. I have been holding onto thousands of cards for years to sell and the market price only gets worse and now if you want anyhting for them (which isnt much)they have to be graded.
The only cards that hold their value are the old cards, unique cards, and cards that are produced by certain companies that dont flood the market.
I feel the turkey call world is in the same boat, but I could be crazy.