This is what I got from the UNSW Union Annual Report. The 2004 one isn't out yet, only 2003, I got my info from note 2 (page 29). It's available at
http://www.union.unsw.edu.au/website/documents/annualreport.pdf
Total Revenue - $19,307,434
Membership Fees - $5,774,815
That means that 70.1% of revenue comes from non-membership fee sources. There will still be some people that join the Union, so say 30% of people join and fees are cut by 50%, that means that the union will be receiving 74.6% of its previous revenues. This means a number of services will be cut or scaled down, but the Union will not ceace to exist.
I really encourage people to actually look up the official numbers for themselves rather than just assume something that you read on page 3 of the newspaper or heard on the 6:00 news. I'm not saying that to push one view or another, I just want to see people informed.
Edit: I forgot to include interest on deposits in my calculations, it accounts for about 1.5% of revenue, so my figures of 70.1% and 74.6% would go up to roughly 72% and 76% respectively.