Whole pile of things up against show promoters.
The most expensive advertising is local advertising. And, without local advertising you wind up with a lean show. Those radio spots, the billboards, they are reminders for people with hectic lives. Cheap radio spot is $500 for a 15 second DJ voice over. Six spots a day for 3 days is nine grand. Radio stations selling $500 spots don't have that many listeners. One billboard for a week runs to five grand, not including the actual graphics.
So, one billboard and one radio spot have set you back ten grand. And, you have to hope enough potential customers actually listen to commercial radio or drive past that one billboard. Promoters who are bad at "exploitation" get a reputation among the vendors at those shows. But, that's where shows charging $80 per table are setting their prices from.
The vendors do not have it easy, either. They need to pack up inventory, often deciding what to take off the shelves in their own brick-and-mortar stores. That has to be loaded into a trailer or trailers, and those want to be stout trailers to carry ammo, and to keep the contents secure. And, the vendor needs a truck able to pull the trailer, too. And all the fuel to get from where they are to where the show is. They basically "lose" all of Friday as a needed travel day. Then, they also need a motel room, or rooms, too. And, they will be buying three days' food out on the road, too.
That's tough sledding if only 30-40 miles across town or the width of the County. When it's 100 or 200 miles, it jumps up an order of magnitude.
There can be an upside for folks with a brick-and-mortar FFL out in Podunk, they can bring their inventory to "the big city" and get more lookie-lous in a weekend than in a couple weeks back at the store. But, you still face all the expenses involved.
And, while we all grouse about the prices on things at the shows-which are clearly not ideal--they do need to be set where some sales take place, or the whole venture is a loss. And there's no guarantee of sales. That grump who needs his 219bumble bee, or a grip screw for his left-handed lever action double barrel pump shotgun, may still balk at the price the one vendor has on the one example of those at the show. And, that grump will grouse forever on about "gouging" afterwards, too.
We in the gun community can be some serious fusspots.