[Dead Corpse]

It isn't the tax that is onerous. It's the fact that there is such a small pool, relatively, of NFA weapons that a $400 rifle is going for $12000 before you start paying government fees.

Also, I need to make a correction to part of my earlier statement. Taking a look around, it turns out the Remington 870MKS is considered an AOW (All Other Weapons) and only requires a Form 4 and a $5 tax. However, it's expensive and Knights Armament won't sell 'em to just anyone. I've only found one person for far that says they were able to purchase one.

[ctdonath2]

You're blurring subcategories and laws.
AOWs require a $5 tax. New ones may be made.
Non-AOW, non-MG items require a $200 tax. New ones may be made.
MGs require a $200 tax. New ones may NOT be made for civvies.

NFA per se is decreasingly onerous. The tax, $5 or $200, is by inflation falling from practically prohibitive to merely obnoxious.

922(o) - often confused with NFA - bans post-'86 MGs altogether. It is ONLY full-auto things that have the limited supply, and thus are costly per high demand.

(FWIW: I have 3 NFA items.)