Alien Colonial Maries Ltd Ed. PS3/ XBOX360 / PC is $29.12 shipped @ Zavvi
Zavvi has Alien Colonial Marines Limited Edition for PS3, XBOX360 or PC for $29.12 shipped to Australia. This is $50.80 off the regular retail price for the PS3 and XBOX360 edition and $27.30 off the PC edition.
The next best price I found for this game, was $31.99 with free shipping at Oz Game Shop. I also saw it at Game Lane for $44.95 excluding shipping.
The discounted prices at Zavvi are only available for a limited period though so get it soon.