saab, no, you don't need to pay to see who will be there. There are links in the guests section of the air, inc website that will get to the current job fair and who will be there.
I have heard that some don't even pay to be at the job fair and being at one this year, I can see where someone could get some face time with the recruiters without paying. Me, I paid. One, because I was using someone else's services. Two, I didn't want to be the guy that got caught and got on some bad lists.
I'm a military guy so I think that helped a lot with being pushed up in the stacks, but I really think that my time at the job fair and who I talked to got me going in the interview process with CAL. I didn't have any internals when I was asked to interview which was only a couple of weeks after the job fair. Delta and NWA came in a little later. All without any internal help other than talking to the recruiters at the job fair.
Hope it helps. I know some will badmouth the fairs and I can see their point in some ways. Me, the $100+ was insignificant in the job search.