>>331651896
>>331649669
Convert your steam account to use USD. Set a US billing address (the forwarding service). Pay with AU CC, ship to service address.

Overall price is whatever the exchange rate of $999USD, plus ~100 GST, 150 shipping, 90 customs and handling. The forwarder I used is an auspost tool, ShopMate. 

The longest delay was in AU customs, everything else was really fast.