I'm aware of the Big Mac Index, having been a reader of The Economist for about 30 years now. It's a little misleading, as it is based on the "rack rate" for a Big Mac all by itself. Who orders a Big Mac and no fries or drink? Still, it's a good comparison if one understands the limitations. An apposite comparison would be to the cost of a meal rather than just the sandwich. You'll note that a large fries, for example, is three Aussie dollars (about US$2.50). Buck seventy-nine in the States.