Book Fairs are important but have for years been losing ground to the internet and an aging audience. An option for revitalizing shows is available to show promoters: require that every participant honor their listing [and or listed] prices and offer a 20% discount for purchases confirmed at shows. Think about it.
Every serious buyer checks the net and everyone who exhibits knows it. So why not cut to the chase? Assuming that material is competitively priced the guaranteed show discount should close a lot of deals. It will certainly increase the number of people coming to shows.
Consider what the advertising will say - Book Fair - every item discounted 20% - Guaranteed. Today buyers expect better pricing on the web but they will no doubt return to shows if incentives are provided.
The more organized book fair promoters may even be able to create unified databases of exhibitors' material. Then, with the incentive of a 20% discount in hand, encourage buyers to ask dealers to bring material that appeals to them. They'll know what you have, come to the show to see it and be incentivized by the show offer to buy it.
Finally, to ensure that no dealer cheats require that any book offered at the show be offered at the dealer's recent online price and be discounted from there. If book buyers can see that the deal is real they will be interested. If dealers have books they are not prepared to discount keep them home.
A well executed plan could bring a surge of interest and the opportunity for dealers to convert books into bucks.