You're paying to be in the sorority itself. It's not like you're not directly paying the members. You're paying to be in what is essentially an exclusive club. And by being in that "club", you make friends with the other members.
By your logic, you being in college is also buying friends. You're paying to be a part of the college, and you make friends through the college...
People who say that girls join sororities because they can't make friends on their own are ignorant. If we're incapable of making friends, how are we able to get into a sorority in the first place? With all the things we're involved in, sorority girls are some of the most social people you will ever meet. So I'm pretty sure we do just fine.
It's basically the same thing as joining a club at school, like Splash said. The only difference is that you pay to be in it to fund the activities done. You don't have to be friends with the other members, but it just so happens that you do make friends in a sorority/fraternity as you would in a regular club.
Because you know the reason everyone chose to join a sorority. FYI, people don't take you seriously after you throw out an ad hominem insult.
You're an idiot. The point is that if you pay to be in a sorority, you're only doing it to have friends because you're not good enough to make them on your own in the real world