After having bought an expensive (is there any other kind?) display case for my Tamiya USS Missouri battleship (350 scale), I, too, wondered why I had spent four times more than I paid for the model itself which was about $50.
One day I was getting cat food in my local pet store when I spotted fish and reptile aquariums for a fraction of the previously mentioned display case...anywhere from $10 to $40....So for my next battleship, the German Bismarck, also 350 scale and 30 inches long, I picked out an aquarium for about $25 bucks, turned it upside down and used a wood panel floor and viola! Ia nice display case! So check your pet stores, guys...