It depends what course you are interested in. Education and nursing courses are the least expensive. Arts is 2nd least expensive. Science is about $6800 per year. Medicine, vet. science, dentistry are the most expensive. Sorry, I don't know the costs for any courses besides science.
Its also different depending on whether people are in FEE or HECS places and also whether unis charge the maximum or minimum HECS per band and so on. Just check the site(s) of the uni(s) you want to go to, in order to see the HECS fees and so on.