In Australia this sort of pricing is a bit of a sore point for many people including myself, and it's even referred to in Australia as the "Australia Tax" in the media.
Rather than using the terrible exchange rates from the Mac App Store (!), why not just sell it in US dollars and let people find the most cost effective way to buy it? For example I have a credit card with good exchange rates and no international conversion fees, which would save me almost $10 over the price you've provided online - for the same product from the same company! If your email says US$39.99, why can't I pay US$39.99 instead of AU$62.99? Even with my bank's terrible exchange rates and over-the-top commissions it would still be about $5 cheaper to buy in US dollars rather than the one you're quoting.
Sorry for the rant, and I know it's still a great price and everything, but it just leaves a bit of a sour taste in my mouth when companies like Apple screw us over on prices and then others like Affinity blindly follow.
Cheers,
Chris