US Store, 17" MBP (no taxes): AUD$3655
AU Store, 17" MBP (no GST): AUD$3999
CAN Store, 17" MBP (no taxes): AUD$3591
You have to add sales tax to the US and Canadian prices as they are not only aren't displayed in the price but the taxes differ from state to state/province to province. Aussie GST is quoted in the price and is that same across the country so a 17" MBP costs exactly the same in every state.
The difference is about $400 which is pretty big but we're not a big market, thus selling to us costs more as the size of the market can't make up for the increased cost of getting the products to us.
We also make more money, I remember a while ago doing a comparison between a waiter on Aussie award wages and US minimum wage in the purchase of an iBook. The US waiter would have to work ~2x as many hours as the aussie waiter to afford an iBook at our respective online Apple Stores.