I don't know about Australia and UK but I know that just recently, the US dollar was right in line with the Canadian dollar. So other than the outrageous taxes they pay I can't imagine why it is SO much higher there. I'm a Stampin' Up demonstrator and the prices in the Canadian catalog are insane compared to the US prices.
When we were in Canada we ate at a McDonalds and for the 5 of us, it was over $30. In the US it's usually around $15-$17.