http://susf.com.au/files/SydneyUni_2011.pdf
^has all the prices for casual/3/6/12 months etc
also, the usu is not associated with sydney uni sports.
there's two gyms serving different clients:
aquatic centre (darlington): lots of cardio machines and weight machines. very limited free weights, 1kg - 30kg(??) dumbells, some barbells and a smith machine. also a lot smaller than arena. weight machines are pretty new (1-1.5 years old)
arena (camperdown): less cardio than aquatic centre. machines are older. lots of free weights, 1kg - 50kg dumbells, 2 lifting platforms with chalk, a lot of benches, a smith machine and 3 power racks. also has metal and weightlifting plates.
both gyms are probably cheaper than most places. can get pretty crowded at times with most sporting teams using arena. can be a bit intimidating at first but both are good gyms.