Probably a bit like all those VHS you used to see on the shelf that were not major films.
Multiple productions across a warehouse. Paid a day's work but credited on multiple pornos.
Good question. I remember a documentary about the porn industry from way back, when Traci (sp) Lords stuck to her guns and demanded $1000 for a film. Well over the top for the time. But they wanted her, so the paid her. That was definitely out of the ordinary.