If you do a little bit of research, you can most probably find some of these parts for a lot cheaper, but if you're the impatient type like I am, you'll pay for it.
The total for the parts I have listed here is $94.17, and there are a few things that I can think of off the top of my head that aren't even listed here: Printing and laminating of the Button Box overlay, wire, quick-disconnects for the button switches, and the A-B USB cable (oh yeah, and tax and shipping for some of the items too). Obviously, buying any of these parts at Radio Shack like I did is part of what drove the cost up, but this should give you at least a rough idea.