I'm Australian but I don't see what's wrong with an Australia tax. If Australians are prepared to pay more for a digital product then it makes sense for the seller to charge more.
Imagine a law that says, "The price of Photoshop in Australia cannot be more than the price in the US". Wouldn't that law be economically similar to one which says, "The price of Photoshop in Australia cannot be more than $400"?