the prize is an Alienware Aurora 7500 system valued at $3,915.99. The system comprises: AMD Athlon 64 4000+ CPU, Windows XP Pro, SLI Motherboard. Saucer Silver Case, NVIDIA 6800GT 256Mb video card (SLI ready), 1Gb Alienware Dual Channel Ram (2x512), 80Gb SATA 7200 NCQ HDD, 16x DVD Rom, Floppy Drive, ViewSonic 17" 8ms LCD display (VGA), Microsoft Multimedia Keyboard, Microsoft IntelliMouse 4.0, Alienware mouse pad, 1 yr RTB Warranty.
Yep, you're right, $4000 (even in AU currency) seems a bit overpriced according to raw value of the components, but Alienware is normally like that for all their pre-made systems.
It's a bit like Nike: you pay some for the brand, you pay some more for the looks, and then you pay a bit more coz they can get away with it.