I would guess the $32.99 price on Amazon.com.au is a typo in the publisher's metadata and it was supposed to be $12.99 Australian. The same book by the same publisher is $13.99 at New Zealand retailers ($NZ incl. 15% GST).
The best thing is probably to email the publisher direct and ask them to fix it, in my experience Hachette is one of the better of the big publishers in that they do actually reply and fix things if there is a mistake.
Be polite, say that you want to buy the book, but point out the price difference between Australia and New Zealand via one of the retailers that makes this easy (i.e. not Amazon or Google) (e.g.
Apple NZ vs.
Apple AU).
(Edit: The reason I suggest comparing the NZ and Australian prices is that the UK, US, Canadian prices are often set by different branches of the company. In the case of Hachette, both the NZ and Australian ebook prices seem to be set by
Hachette Australia.)