This is the cheapest I have seen for this game, I saw it on sale in EB Games for $50, and here you can get it for less than $20 shipped. Also the game is region free so it will work on any console.
Please note that the link is an affliate link. However if you wish not to use the affliate link you can go to the item directly here if you wish: http://www.play-asia.com/paOS-13-71-dw-49-en-70-38zh.html
Some other awesome deals below if you are interested:
Ninja Blade - US$ 19.90 (~21.87 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Ninja Gaiden 2 - US$ 24.90 (~27.36 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-dh-49-en-84-j-70…
Condemned 2: Bloodshot - US$ 14.90 (~16.37 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Command and Conquer: Red Alert 3 - US$ 14.90 (~16.37 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
HORI Fighting Stick EX2 - US$ 56.90 (~62.52 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Kane & Lynch: Dead Men - US$ 24.90 (~27.36 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Batman: Arkham Asylum - US$ 49.90 (~54.83 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-dw-49-en-84-j-70…
Mass Effect - US$ 19.90 (~21.87 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Tom Clancy's H.A.W.X. - US$ 19.90 (~21.87 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Too Human - US$ 14.90 (~16.37 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…
Viking: Battle for Asgard - US$ 14.90 (~16.37 AUD)
http://www.play-asia.com/SOap-23-83-34cm-71-f7-49-en-84-j-70…