From my experience, Bankstown is easy and Paramatta is impossible.
At UWS there are two types of car bays: yellow or blue. Parking in the yellow bay is considered 'general' parking, costing $100 per yea IIRC. The blue parking is considered more prestigous as it comes with many benefits, ie. you can find blue bay parking more easily, its closer to buildings, less walking. It's $400 a year IIRC. These permits validate your parking for a whole year.
Free parking on Bankstown campus is possible provided you kerbside park outside the campus, near the houses. But the walk to campus is dreadful aha.