As someone who works in a museum gift shop, I get the question a lot. "Why don't you have a reproduction of this thing that's on display." Mostly if we do exhibit related stuff its only for our permanent history galleries. The rotating exhibits..? Whew. It costs a LOT of money to reproduce and it requires large quantity orders. The shop has to pay for and cover our costs by ourselves. Where other departments receive a budget for the year based on projects, we have to actually make our budget money back.

So, producing 5 - 10,000 of something that's not on permanent exhibit leaves us with stuff we'll never sell. Its harder than one would think to find related items. We try to stock books/dvds related to current exhibits because we aren't stuck with the inventory when an exhibit closes.

If that helps explain the logic of a gift shop. Unless you're like the Met or the Smithsonian, its hard. :(