I went into Diego's store, and he had like two of them, a blue one and a green one. I was thinking about buying one, but I didn't because I couldn't find any information that explains what they're actually used for.
What are they for? Are they a random shipping thing, or have some use?
I guess, if you've got money to spend and you find a design you like, go ahead. It's a nice little touch; doesn't do much, but makes it a little more realistic.
But I'm really cheap, and I rarely like spending that much money (500 G) on something that doesn't serve a greater purpose. But it really isn't that much, once you become successful enough that you're making enough money to cover the cost.