UnSub on 20 January 2011
Some of it is agreements with Steam not to sell the game cheaper than can be sold in physical stores.
In Australia there is no goods and sales tax on items worth less than $1000 through import.
Exchange rate it at partity with the US (which is why it is curious that Sony is charging Australian players US$20 a month to subscribe to DCUO while it is US$15 everywhere else). So, we should be paying US prices, but aren't for most new titles.
