Sometimes I wonder who buys this shit. Maybe I'm just a total cynic.
Collectors, cosplayers. Also, when you see it in the shop, it looks like a really good idea to buy it. I bought three Bioshock 2 Adam syringes because they were at a reasonable price ($20) and looked cool. Only later did I realize my mistake...
The costume thing is really the only thing that this makes sense for, to me - it doesn't seem like the sort of thing that'd be particularly cool looking just sitting on a self. And really, just buying all your costume pieces pre-made like this kind of defeats the purpose. I find it far cooler when somebody builds their own costume and accessories.
Well if you did some custom paint on it, it would look better. If you make it look actually metallic and set it up so you can see the assassin's symbol. I think it would look cool on a shelf. Put that Assassin's American flag behind it and you got yourself a theme.