You need to get a step up/down transformer in addition to an adapter, try to get it in the US, its a lot easier to find in the States. I would agree that electronics are a lot more expensive in Oz than in North America, new cars are also pricier and leases are only available to business and self employed people.
The Aussie Dollar was very strong lately, making things more expensive, the normal value is usually 1 AUD = .75 US cents.
Definitely do not bring any food items, if customs checks your baggage and you did not declare it, you could get into big trouble.
Laptop, Ipod, and other electronics are a good idea to get before going to Oz. You also might want to get the book list from school and try to get second hand copies from Ebay, I was at UNSW for a year, and thought new books in Australia were very expensive.