Australian VS pricing is about 160% of USA VS pricing.
Our exchange rate is currently sitting around 105% of USA's, and has been for a long time.
The product is provided electronically and supported from USA, so it's not as if MS Australia actually does anything or has any costs to cover.
VS USA Pricing includes taxes, so even the argument of our local tax seems a red-herring.
Edit: The inference is that Apple, Adobe and MS are all running a scam to inflate Australian prices across the board, effectively negating the 'competition' argument.