I have a couple of Marchetti and Longe machines from the 60's. You might be surprised by the level of sophistication of historic shops. I have read that Raleigh had 600 punch press machines running at once and it took 125 operations to make a BB shell. All with a punch press. It would be interesting to see what time it took to build a Raleigh professional compared to a modern Trek top-end road bike.
I am into the older bikes for riding performance but build TIG welded aluminum frames for a living.. go figure.
If JohnDThompson or a brazer with short-run experience gets in on this, we would have a pretty good idea. From clean mitred tubes to load and tack about 10 mins (if the tubes were already fitted and the fixture was hard-tooled) . I can fully TIG weld a high-quality aluminum frame main structure in about 25 mins. I stick on all the small parts on and 'send 'em home in about 15 mins. This is not rushing either but it is say, an order of three to five.
I am not sure we have made huge progress. I am open for debate.