Was going to reply in the Private Flying forum but since you moved it here...
I did some flying (ASIC, license conversion and all) in Oz a couple of years ago and yes, it is expensive! Due to the forex rate, pretty much everything costs an arm and a leg, not only in aviation, where one tends to expect it
Of course it depends where you are going and what you'll be flying, but the figures you quote are, alas, not totally out of line. Have a quick look
here, they are a reputable outfit (I did not rent from them, but visited and the a/c I saw looked in pretty good nick).
Enjoy Down Under, but be prepared for the plastic to melt
