Until EFI replaces BIOS (Which, last I read, wasn't happenning until about 2008-09), the only way you can "build" a Mac is to use a booting hard drive image that uses EFI within its own boot loader.
http://www.uneasysilence.com/os-x-proven-hacked-and-running-on-an-ordinary-pc/
Your milage may vary.
As for Apple hardware being a waste of money, Apple grooms their hardware designs to work and be esthectically pleasing, as well as easy to work with on the inside. Most PCs I still see today in mass production are generically designed with minor tweaks applied to the case, i.e. ATX. Sure, specialized companies like VooDoo may use UV reflective plastics, tubes on the cables etc., but they don't have the control over their designs to alter the motherboard to their tastes.
You pay for what you get.