Imagine my surprise while flicking around the channels that a show called How It's Made did a segment on Perry Miniatures and how they make metals and plastics.
The metals I kinda knew thanks to a trip to GHQ back in the late 1990s. The plastics I had a general idea, but the show did a good overview of the process.
Starts with the wire model built up with green putty (Perry does it using his custom prosthetic) then heads into metal casting.
As for the plastics, the creation of the steel mold is a labor intensive, multistep task using milling machines/processes and so to create the mold. After that, the plastic frames pop out (four at a time, I think, or maybe six, it went by quickly) in a couple seconds each. Boxed and packaged like you see in a store.
I don't know the episode, or whether I was watching a new one, or as I suspect, a re-run, but a Google search may turn up the episode. Maybe, maybe not.