Lego REALLY overprices custom made stuff.
EDIT: Add a bit more...

Just so you guys understand why the ribs are backwards, I'll tell you what I'm making.
I'm making a tank out of this skeleton. The head will have the barrel shoved through it's mouth, and possible more weapons. The back with the ribs will be a transport container, and I plan the have the hipbone as the opening door to get in it.
I don't know how I'm going to attach wheels, or a custom tread, but I will.