I want things that are rare and I certainly don't have more money than I need. Some people just like rare things. I'll frequently take a custom product or a 1-of-1 over a standard option assuming the price isn't vastly different. All the art in my gaming area is commissioned and it's not much more expensive than buying and framing a print. The custom side art on my home-build MAME cabinet was only $200.
Some people like knowing that not many others have something. Scarcity definitely sells.