http://www.pcgamer.com/steam-will-display-australian-dollars-soon-according-to-developer/

Using Steam isn't much fun in Australia. All prices are displayed in US dollars, which means checking conversion rates. And because the Australian dollar has been a bit up-and-down compared to the US of late, it's getting increasingly difficult to make a ballpark estimation on any game's price. Oh, and sometimes the price on Steam ends up higher than what Australians would expect to pay at retail.

But it looks like Steam will soon catch up with the likes of GOG soon, despite promising it would happen back in 2014. One studio has let slip that it might be happening in a matter of weeks.