It's the same as most other campus organization, you pay dues. But I can break it down a little bit as to what the money goes towards. It goes much deeper than just a club on campus. Greek organizations have national headquarters with full time employees. The dues go to things like social functions, philanthropy projects, officer supplies, housing dues, headquarter fees, GPA rewards for members, etc. On my former campus, sororities had large houses that had to have the bills paid and a full time staff for each house that had to have their salary paid. This was shared by the members of the chapter as well as the University. Members are also on a meal plan and get cooked meals twice a day at the chapter house. If you're a member of the chapter you also have the option of living in the house, and you pay on your tuition the same as you would if you lived in a dorm.
I can't really speak to the "segregation" of hair colors you mentioned, but I can tell you my experience was nothing like that. No one was ever judged or selected for membership because of a physical attribute. I was never singled out or put into a group for being blonde/brunette/overweight/underweight/southern/northern/red/white/black/brown. Chapters ask girls back round by round after getting to know them and learning about their personality, interests, hobbies, passions, etc. It's also a mutual decision, with girls having equal input on which houses they want to return to. I'm not ignorant however and won't deny at some schools it can turn superficial, like in the case posted above at Bama. It's a very sad situation and I'm glad it was brought to light. Very few chapters at very few schools are run that way, and I think I speak for all Greek Life members when we say the sooner that kind of thing can be eliminated the better. It gives people the idea that that's all Greek Life is about. I believe that's kind of the idea you bought into here and I hope you can take the time to see that that is certainly not the case. My sorority offered me leadership opportunities, friendship, networking, life skills and (as cheesy as it sounds) memories that will last a lifetime.
If you have any further questions please don't hesitate to PM me or ask anyone on here. My Greek Life experience was honestly life changing and I love to help further people's understanding of what it truly is!