when I teach innovation classes we talk about the difference in mindset between making 1, making 10, and making 100 of something (and obviously this would scale to 1000+ but that is kind of beyond a lot of students). Until you have experiences with scaling manufacturing you have no clue.
I used to do consulting work on this (my background is in manufacturing). Typically I would come into a company at the prototype stage and work with them to redesign the prototype to make it manufacturable...I loved doing it but wow does that mindset have to change about what can be accomplished. There was an article on HN a while back about why you can't manufacture like Apple that I really should have saved, it makes this point beautifully.
This is a key component in why hardware start-ups are hard. Proof of concept: dead easy, as long as physics does not make your product impossible. Prototype: a little harder. 0-series: already quite hard (that's roughly what the story above was about). Mass manufacturing: super hard.
It's also why manufacturing samples should never be taken as indicative of what a plant will actually put out and you still need to sample the actual product to determine if quality is acceptable or not.
Lots of companies doing business with third world producers have found this out the hard way. (And then there is malicious substitution as well to content with.)
And requires skill sets that seem really similar but are not actually all that similar. They are linked through engineering design but yeah...they aren't.
I used to do consulting work on this (my background is in manufacturing). Typically I would come into a company at the prototype stage and work with them to redesign the prototype to make it manufacturable...I loved doing it but wow does that mindset have to change about what can be accomplished. There was an article on HN a while back about why you can't manufacture like Apple that I really should have saved, it makes this point beautifully.