Plenty of vehicles only have production runs of ~10,000. At those scales, you really don't get economies of scale. In fact, there were only 25 car models that sold more than 100,000 units in 2021.
Plenty of particular brands of vehicles have smaller production runs. But "vehicle" to the manufacturer doesn't mean "brand". It means "set of pieces and parts that can be the same or nearly so across many brands". For example, a "Cadillac" to you is a different "vehicle" from a "Chevrolet"; but to GM, the vast majority of the pieces and parts and manufacturing processes are shared. So the economy of scale to GM when building "Cadillacs" is huge even if to you it looks like "Cadillac" has a small production run.
Exactly, and this is one of the reasons modules need programming, because it comes “virgin” with only a bootloader and the features are loaded according to the VIN.
