I have over 15 years of experience in consulting all kinds of companies in this industry (big and small).
There is not much to add for me to the start-post to be honest.
I can't disclose many companies because of NDA's, but yeah the majority of them don't do much inhouse.
I personally find point 7 about "sophistication", spot on!
One thing the topic started probably also ran into, is how much better off big companies are when everything can be done in bulk.
The competition is quite uneven in that regard.
That 30% number plummets, so badly that labor is often orders of magnitude higher, that also counts for high-end products.
This is also were many startups struggle, scaling up from a nice (and sometimes awesome) idea, to real production.
Since this really changes the company of "developing" something, to producing.
Many many years ago, the real eye opener for me, was when I dove into some books about how marketing actually works.
Seen from a science and psychological point of view, not from a business point of view.
If anyone here really wants to understand how speakers and acoustics work in commercial products, those books are an absolute must read!
For example, what most people (here) don't realize at all, is that there are a lot more priorities than just plain and raw "audio quality" (whatever that even means).
That seems obvious maybe, but it also doesn't seems crossing a lot of people's mind judging or even reviewing those speakers or other audio equipment.