Which sites do providers have to pay

I went on Tris just to see what it's like and it looks like I would have to pay something. Anybody know what that amount is and is it worth it? The other good recommended sites are any of them free for providers?

I thought the same thing on tryst but they do have a free membership as well. I've gotten a couple calls from there in the past year but I don't do much w/my profile.