It costs me about $30/week. That's pretty much all transport costs, and I rarely buy food at uni. There are one-off costs of textbooks, fees, etc so if you average them out then you get something around $50-$100. It really depends which uni you go to (for transport), where you get your food from, how much uni fees are, how many textbook you need to get and where you get your textbooks from (2nd hand, not at all - ie. go to the library or borrow from friends).
You can save a lot of money by just being money smart and shopping around. I take all my food to uni, get my textbooks second hand whenever possible (and in one case, not at all) and go to all the socirty BBQ's (that includes societies I'm not in
).