It's been done! A Mac Clone: $399

Check out the Hackointosh: Psystar Corporation - Open Computer. "The highly extensible Open Computer is a configuration of PC hardware capable of running unmodified OS X Leopard kernels. If you purchase Leopard with your Open Computer we will not only include the actual Leopard retail package with genuine installation disc, but we also include a Psystar restore disc for your Open Computer and we will preinstall Leopard for free so you can begin to use your computer right out of the box." Base Configuration 2.2GHz Intel Core 2 Duo E4500 Processor 2GB of DDR2 667 memory Integrated Intel GMA 950 Graphics 20x DVD+/-R SATA drive that is Lightscribe-capable 4 rear USB Ports