Like other cloud services, AWS is usually paid for by credit card — but since the fees are in US dollars, you can end up getting slugged with conversion fees. You can now avoid that by setting Australian dollars as your preferred currency.
The Australian dollar is one of 11 new currencies now offered as a "native" option by AWS (New Zealand is also on the list). If you change this preference in account settings, your bill will be converted to Australian dollars at a "competitive exchange rate" before being charged. Right now, $1US is being converted to $1.298 Australian, which is fairly reasonable.
Note that the basic rate for AWS products will still be set in US dollars — we won't see official "local" pricing. This option also only works for Visa and MasterCard; if you're using a work Amex card, you'll have to stick with the US dollar option.