Couple minutes ago I finished a 1968 Criterion documentary called
Salesman, also known as The Thing David Mamet Watched Right Before He Wrote Glengarry Glen Ross, and it hits all the same notes.
Four chainsmoking door to door salesmen are selling overpriced tacky bibles to Catholics who cannot afford it. They buy their customer list from churches and then bang on doors to make the argument that their lives would be better if they had a bible that costs $350 in today's money. Obviously none of these families have that kind of money on-hand, so they pay in installments. The bible salesmen then also work as collectors, and they charge a vig.
It's filmed in black and white, which is appropriate as the movie is bleak as fuck. The salesmen are all piled together in a shitty hotel room, spending a 10 week stretch away from their families as the drive around Florida burning down their customer list. When they manage to get in the door, the prospective customers look beaten and sad. There's no joy in the prospect of them owning a tacky bible, just the looming debt that this proposition brings. Every sales pitch looks more like a police interrogation than anything else, the salesmen with unbreaking focus on a person who never makes eye contact, just hanging their head and answering softly, hoping that they can just keep saying "no" until the bad man goes away.
The movie looks as old as it is and the low budget is also quite visible, but I think that works in this place. The visible camera and shabby production values just help to make the thing seem desolate and claustrophobic, and there's no voiceover or interview or manipulation or artificial story arc. Just "Hey, this is what it is". I really prefer that in documentaries - if your subject is as interesting as you say it is, it should be enough to film and edit. And in this case, I think it was.
The same guys also did that
Rolling Stones movie about the Hell's Angel murder. I think I might watch that next.