That's basically it in a nut shell.  The big thing that the promoters care about is renting tables to the exhibitors and don't care who it is or what they sell as their money is as green as anybody elses and they talk up the event as a "gunshow" to get the locals in the door...more $$$ for them.  As long as they keep renting out all the tables they could care less how many gunshows they promote, and the couple others they're in competition with, or when they are compared to others as it's still a cash cow for them.  You don't see people writing checks or putting their entry fee on CC so yes it is literally a "cash cow" with no actual numbers known how many people entered that day/weekend...think of it as a waitress who makes most her money on tips (cash) and is supposed to, by law, claim a set percentage on their taxes.  

Ok, I've stepped down from my soap box.