One basic answer is economies of scale. Australia has three cities over one million spaced 1000km apart. Total population over whole of Australia 23 million. USA has twenty or so cities over 1 million. Total population USA is 313 million from wikipedia. Economies of scale.
Also you got 25% off retail. There was no fat left in the deal for the retailer here. Also we are a more socially just country than USA. $21 casual rate for retailer. USA's is $7.50, with very limited free health care. I would rather live here and pay a little extra for a little extra social justice.
