It fascinates me, that volume and automation can make this profitable. Very nice article and I would love to see a cost breakdown of a PCB manufacturer. There is still labour involved in manual handling and even communication with customers.
In contrast, even today, sending any level of drawing to a machine shop at the time would have immediately resulted in a phone call to talk about exactly how I wanted something made, and why it couldn't really be made that way. While there are "quick turn" shops that can work directly from files, it's definitely a more recent development.
Even though "Gerbers" were a deeply primitive format, they got the job done.
At my workplace, one of the old-timers showed me the automated wire-wrapping machine, long since retired, on its way to the scrap yard.