My parents, especially my mom, was dead-set against me joining a sorority. She had that typical sorority stereotype in her head. My parents also would be the ones paying the dues, but I knew it was something I wanted.
My advice...sign up for recruitment. Explain to your parents what the sororities at your school are--their philanthropies, etc. When you go through recruitment, they should have a breakdown of dues (usually, if not, ask for a ballpark estimate) and then give that to your parents. Yes, the first year is HELLA (lol) expensive, but its totally worth it.
If after you discuss this with them, and they still are adament about not paying for it, or whatnot, then you can drop out of recruitment. I know its not the best way to go about it, but that is what I did. My parents saw how committed I was to making it work, and my mom finally told me that it would be something good for me