The problem is having a dedicated professional buyer, who's worked out what's needed to clean up, at what's basically a relaxed social scene for enthusiasts. Yes, some people have their eye to business and a lot of the stuff probably winds up on ebay, but he's taking it to a different level. You have to ask questions, because this can't be much of a profession.
I've been to a BVWS event as a stallholder, and there was a lot of inter-stall action before people were let in. The auction was mainly a load of domestic stuff, old tellies, domestic radios and like that. I'm sure there was some test gear. Just the place to go it your idea of an RF sig gen is an Advance H1. It may have changed, that was a long time ago. Professional valve dealers latched onto it. People going there to cop a pair of PX4s for their 1930s radiogram, hoping to get them for £20, perhaps going as far as £30, found they were bidded out of sight. These valve dealers may not have been entering into the spirit of things, but they weren't doing anything wrong.
I also went to the bashes at the NEC. You could pay £15 extra to get in before the crush, which I did, and snagged some bargains. If you have stalls, it's hard to avoid the problem of the bogus stallholder, who's really a buyer.
I've also been to a Radiophile auction years ago. It was a silent key sale of the estate of a very dedicated collector. There was a huge amount of stuff. Some of the lots were far too big. There was a palate of AR88 spares, including NOS O/P transformers. The professional auctioneer got fed up and started to bundle things together, offering them to previously successful bidders for the same price. A valve dealer outbid everyone on a lot of 25 NOS 5Y3GTs. I was glad I went there because I scored some real bargains. I came away with the feeling that it hadn't been entirely satisfactory.
To cut an already overly long post short, I don't see how radio rallies can be turned into auctions. It's not what they are about. It's a shame the Demon Buyer takes the gloss off it for some of us, but there we are.