Yep everything's going to be crazy expensive - but on the plus side, wages should be decent if you're looking to work while you study. Also, I don't know what public transport's like in Perth, but if it's anything at all like Sydney, you're going to need a car if you want to get anywhere.
edit: also - get used to people shortening the names of EVERYTHING and adding -'o' to the end of words!
Sydney public transport is so good compared to Brisbane. At least in the inner city.
Anyways, it's all true with the living costs, things get pretty crazy expensive here. There's a reasonable "scene" going around in most major cities, though be prepared for some douchey 18-year old crowds and older kids that need better things to do with their lives. Learn to recognise songs by Parkway Drive, The Amity Affliction and The Getaway Plan or else you will look obviously foreign.
Try not to get into the whole festival singlet look. It's not classy.
Wear sunscreen. Lots of it. There's a hole in the ozone layer and not only will that make you burn faster, it also heightens your risk for skin cancer.
Vegemite is gross. Tim Tams are yum.