A partner and I did show photography for three years and the above quote is part of the reason why we stopped.
I literally had a mother tell her husband “Go stand next to her [me] and take the same shots she does–then we won’t have to pay.” I had other spectators get in my way/in the shot trying to grab the same capture so they wouldn’t have to buy photos. Most disappointing of all, though, was the “friend” who was a decent photographer with good equipment who would post all of her photos from the shows online for free.
We would shoot from 7am to dusk every day at four-day shows–in the heat, in the rain, in the dust-- come out with literally thousands of frames to process, spend a week at home processing them, and then have people complain about the cost (which was actually at a loss for us by the time you factored in hotels and food and the like) and the time it took to get photos posted for sale.
It was very rewarding to capture great images and moments and have people really happy with the results, but you really have to love the work.
All of that said…I really like the idea someone mentioned below about working with one client (or two) to capture their day at the show. That seems like a great way to make an impact and also not kill yourself for pennies.
I highly recommend Lightroom for post-processing. It has great capacity for organizing large batches of images, is more intuitive than Photoshop, and interfaces with services like Smugmug and others to upload directly into pre-made galleries. Very handy for coping with the kind of volume you can generate at a show.