I asked my sister's boyfriend if he was in a fraternity in college. He said, "No, I don't pay for my friends." Both of my biological sisters looked at me like

! I thought that it was funny and laughed. He's a nice enough guy, but he doesn't really know much about greeklife. I really don't get offended by remarks like that. I think that they are usually a joke or a reflection of ignorance.
When I was a student, I paid my dues which went to National, the campus, and to chapter operating costs including social, sisterhood, and service events as well as postage. I remember I had over 45 sisters, and dues meant that I paid less than $3 per sister per semester. That's a bargain! And it included my formal ticket.

A date was extra and optional.
Don't worry about it when people say things about paying for your friends. You know that it isn't true. You don't need to explain yourself to anyone. It's not like you give each sister or brother money to be your friend. I'm pretty sure they know that.