So my workplace tried changing my roster from 6am to 6:30am start and end half hour later. The problem with this is I would be missing out on half an hour of penalty rate each day. I took the proposed roster change to my union and they helped me to dispute it. Unfortunately there was no opportunity to leave the roster as is but we found a resolution which involved working an extra hour on Sundays to make up for the lost penalty rates. This resolution means I don't lose any money (I actually end up about $2 per week better off). I added up how much this was worth to me over the course of 1 year and it would have been almost $1000! I'm not thrilled about having to do an extra hour on the Sundays if I'm honest but it's a lot better than losing that 1k by the end of the year. That's literally my holiday money… Union fees do cost me about $400 per year mind you, but I'm starting to see the benefit of why I joined up now as it's benefiting me in the long run. The fees are tax deductible too so that $400 becomes more like $200.
So yeah don't be put off by union fees, they're worth it. When your workplace tries to screw you over they'll fight for you. You just gotta stick up for yourself and don't be afraid to ask for their help.