I find it humorous how much machineguns come up in an NFA discussion, because that's a small niche within a small niche within the larger firearms community. As Yugorpk said, "when 200$ was real money it was rare to see anything NFA." Well, when a clap-trap MAC pistol with no practical use but noisemaker runs over five grand & there's fewer left every year, well...
I think the real reason NFA is booming (especially for SBRs, which, let's face it, is a pretty poor use of 200$ from a pure cost/benefit viewpoint), is because the trust system has circumvented the intended practically unusable nature of the possession rules. Now that it is possible to get the whole family their access to your gun without a weekend trip to the sheriff's office to get printed like criminals (Yippee! My favorite!), and others can be added/removed from that access at any time without consultation of the Bureau, the 200$ and months-long wait can be tolerated more often.
The reason I think this is the real reason for the boom, is because the administration is so hell-bent on putting a stop to it with 41p. If you have to get everyone printed, everytime you submit a stamp application, and have to get prints for every new person you give access, things get both complicated and expensive (and impossible, in no-sign jurisdictions). The administration sees how silencers are getting mainstreamed, as well as SBRs, and are desperately trying to head us off at the pass.
"The chicken bone in the throat is the rotten Hughes Amdt that has made full auto a rich man's game"
Import bans on cheap ammo 'helped.' I wouldn't even use a MG if I owned one, at this point; it'd be like a birthday and New Years thing, and that'd be it.
"The NRA is perfectly prepared to throw MG owners under the bus, if it serves its purposes. Witness what happened with the 1986 FOPA and the Hughes Amendment."
Well, at this point, MG owners are basically already under the bus (and any further widespread action against them will disproportionately affect very well-heeled doctors & lawyers, so much like Cayman Islands tax loopholes, the status quo is probably pretty stable at this time) so it honestly doesn't cost them very much for the NRA to say such things; that ship has sailed. And as bad as FOPA was, it's like you said, that it happened because MG owners have no representation. There's only so much you can do for a tiny group like that when a majority or near-majority goes on the warpath, and your resources are finite. The NRA did the right thing at the time, their failing is that they have not worked to reverse that tactical retreat since their rise back to prominence. At some level, the NRA is still a 'sporting' association, and MG's --due solely to their rarity-- are not viewed by hardly anyone as a sporting weapon (not even many MG owners). Hopefully, the normalization of silencers, SBRs, and the new resurgence of SMGs (PCCs) will get machineguns back in the mix, with reality shows about subgun competitions leading the way.
TCB