Almost all the shows I enter have an entry fee. The shows use the entry fee money to promote and operate the shows, pay the staff, and pay the juror fee if it's juried -- all this stuff costs money, and sometimes the point is to raise some extra money for charity.
I've worked as staff at craft fairs and art shows... working as staff is a more sure-fire way to make sure you take home some pocket change, you get paid hourly, pretty close to minimum wage. I wouldn't want to do that every day, but once in a while it's fun.
For me, there are two reasons to pay to enter an art show: (1) to sell my art, and yes, I've sold art through these shows, and (2) to win prizes -- it's an ego trip to win ribbons, plus you can tell people you're an "award-winning" artist.
When you buy my art, you are officially buying the art of an "award-winning artist." How's that for showing your friends you have sophisticated taste? That couldn't happen - me gettting to call myself an "award-winning artist" -- if I hadn't entered art shows that offered ribbons/awards as prizes.
Occasionally the jurors provide juror comments on the art they review, so sometimes you get a mini-critique, which is helpful if you agree with the juror, and not helpful if you don't.
The best way to figure out if a show is likely to accept your work, and/or your work is likely to sell at a given show is to attend it -- and talk to the artists and/or staff to see if their work is selling at that venue. Many shows are annual. You go one year, as a visitor, then you decide whether to enter the next year -- and, having seen the show from last year, you'll have a better idea which pieces of your art to select for entry this year.
Obviously, you look at the entry fee, and if you can afford to pay and have all the work you entered get cut (which can happen), go for it. It's a good idea to enter more than one show, because sometimes you get in, and sometimes you don't... it can all be a matter of how many people entered that year (if a lot of art gets entered, a lot of art gets cut -- it can be a numbers game).
