I dunno about other companies, but Canon does "cellular" manufacturing rather than having huge lines all dedicated to just one thing. Each cell is 5-or-6 small

I dunno about other companies, but Canon does "cellular" manufacturing rather than having huge lines all dedicated to just one thing. Each cell is 5-or-6 small reconfigurable stations manned by a couple of people, who build a body or lens from start to finish, rapidly re-taskable to different lenses or bodies on the fly. Hundreds of cells on a manufacturing floor.