Big cost involved. May be due to the location or having to pay speakers?? I've been to an Australasian Society of Zookeeping conference which had an almost identical 3 day layout and including accomodation and food (breakfast x2, lunch x 2) it only cost $420. The gala dinner was an extra $70.
It would be a great 3 days no doubt. Given what i imagine the cost of accomodation in Cairns would be like, on top of the already high price, i imagine only the very dedicated, well off or big wigs will be attending.