I have a 3-1/2" vise my dad made in 1939, from a rough casting, it was finished on a shaper. I can still see the shaper steps on the long rail sides and piece parts. I think it was a university trade school for engineers.
Shapers seem to be so rare from the scrap drive where horizontal millers became vogue, and those left, the seller knows they have value as a rare quality machine tool, and they start becoming 'priceless'.
Not personally having operated one, I can't see what special operation that I need performed in my repair of "things that should be thrown away" hobby. There probably is one, like a deep blind internal spline, I just have not seen where I would have to replicate such a thing with the low grade junk I repair.