I think promoters at all levels need to start looking at the convention scene as a whole to see what's happening.
I live in Philly, and the number of shows within 2 hours of me is astounding. They range from small VFW-style marketplaces to the big multi-day extravaganzas, but I could go to (or set up at) a show every weekend if I wanted.
Now population density is crazy here -- check out this map to see -- so the area can support it mostly, but I've seen that sales and attendance have gone down because of frequency. And while it's not the end of the world when you have a crummy sales day when your cost is $60 for an 8-foot table, it is when the booth is going into the hundreds and thousands of dollars.
Also, this show has no website (just a Facebook page), no information on parking, no times for when it's open, no information on dealer tables... It's sort of a cluster@#$#.