What drives up quality is cost of defects to the manufacturer. Cost battlegrounds change over time. Currently, some of the big ones are in electronic parts elimination and reliability.
> It's rare to see a transistor opened up today to see what went wrong.
Literally everyone cuts open their electronics nowadays. You don't see it because there's no longer any need to complain about it.
It's time consuming expensive work though, so smaller places just replace the faulty parts or revise the design and hope.
You forgot the part where the customer is ready to pay the money for quality.
If it is the bean counters who choose, then they are buying cheap for the sake of cheap.
There are plenty of cases where adding an extra "9" to the end will significantly increase the costs, but there is also a lot of low-hanging fruit that stays low-hanging because so much purchasing is low-information.
Hence why the original comment you replied to requires a "big, hardass, customer." Small customers often cant amortize the NRE across enough products to determine quality, so even if they are willing to pay 2x on a part for it to be better, they don't know if they are getting something of higher quality or just something with a higher markup.
The "big hardass customer" buys enough product to have a reasonable expectation of effecting change in the suppliers, so running both the experiments suggested by GP, and performing post-mortem analysis of failed components can be expected to steadily improve quality over time.
[0] https://www.goodreads.com/quotes/72745-the-reason-that-the-r...
Where this is going a bit nuts is that that it's hard to make 100 gold contacts last for 1000 compression cycles at 1 dppm (better than 6 sigma!). That requires a lot of excess maintenance on the test infrastructure! That will be expensive... and your assembly connectors/SMT is likely orders of magnitude higher defect rate than 10dppb so it won't improve final assembly performance.
Also, I think you need another 9 on that 99.99999% to hit 10ppb and realistically 2, if you want to have an acceptable yield rate, and 3 on the test equipment since they are used 10k times every day.
> Actually, 1000dppm (99.9% defective parts per million) is not acceptable except for hobbyists.
Exactly: There are many more hobbyists than manufacturers, so most people are content to pay lower prices for lower reliability.
If I buy a million parts, I'm probably paying for an acceptable (to me) failure rate, which is probably negotiated as part of the contract. He who buys cheap, buys a higher failure rate.
What really drives quality up is a big, hardass customer. Back in 2018 I commented on the USAF Reliability Program.[1] The USAF was finding out what went wrong with their electronics down to the level of opening up transistor cans to see what went wrong. They were naming and shaming, with press releases to Aviation Week about bad components and who made them. Parts got a lot better.
[1] https://news.ycombinator.com/item?id=18007339