Well, I guess I qualify as a crusty old guy so here are my comments. My first NFA of any type was a PIAT purchased in 1966 or 1967. It cost $6.00 to buy and $12 to ship via Railway Express. Of course, it really wasn't NFA yet as destructive devices didn't need to be registered until the 1968 Amnesty came along. I was too young so we registered the PIAT in my dad's name.
More to the point of the original question, my first Browning machine gun, a 1919A4, came in early 1977. I really couldn't afford a C&R gun at the time which might cost $1000 or $1200, and hadn't seen any offered in my area anyway. At the time, there were only a few side plate manufacturers, the best of which was Chuck Hudak of Inland Arms in Austin, TX. He would sell whole guns and for a while offered a stripped registered receiver option for about $660, if I recall correctly. It was still too much for my budget but he agreed to do some trading to help get me into a gun.
In those days, a couple of ship scrappers were busy in the Portland, OR area wrecking out surplus WWII ships. I used to haunt those yards and picked up as much gun scrap as I could afford, often picking up M2 tripods and new in the grease belt loaders for as little as $5 or $10 each. So I shipped Chuck as big a pile of Browning parts and accessories as I could afford to send, and a couple hundred dollars, and he supplied the missing parts and basic receiver to build me a gun.
The best part was his appreciation of my interest in the history of the 1919 and the fact that I wanted a specific look. While most of his customers wanted the latest and greatest versions of the parts, I wanted a proper "1942ish" looking gun. So he built one with the 3-pc tapered muzzle bearing, non-adjustable front sight, aluminum pistol grip, bolt hold open bar, top cover with riveted rear block, bright metal internals, etc. Pretty much all the early features were necessary to me so I was pretty retro before the word was even coined. I finally found a C&R Saginaw 1919A4 dewat locally and bought it in 1984 for about $550. It was the gun I'd been searching for 10 years earlier but couldn't find. The 1917A1 came along in 1997. Of course, I still have all of them today.