As part of their Midweek Specials, GamersGate have South Park: The Stick Of Truth at 50% off.
This equates to $30AUD. Using Hola, you can get it for $20US (USA VPN). If you received a 20% off coupon recently, this makes it $16USD
If you didn't get a 20% off coupon, it appears to be only somewhat unique, so you may be able to get it working.
For me it's this: NOV2014-7G3EL3L-QPG16RS- followed by the first seven letters of your username.