Earlier quoted context omitted.
With these low volumes the sound move would be to buy chips from someone else. Just like Aston Martin is sourcing engines from third parties. Heck, even Mercedes is using Renault engines and BMW used Peugeot engines in Minis for years. And engines are a core competency of both, BMW and Mercedes. Chips for Tesla, not so much.
The thing is that no one makes a chip like Tesla wants that is tailored to their workflow. Tesla, by going with the 14nm process and inexpensively licensing core IP (i.e. for the ARM cores) and only customizing the NN portion, is able to keep chip dev costs low enough so that in the end they're saving a little money on unit costs, getting a power/performance benefit, and as a bonus is building in-house expertise that…
Aside from some potential benefits down the road coming from proprietary chips I don't see why Tesla would do it. Also the use cases are so similar that the use of in-house chips will hardly be a competitive advantage. So why burn additional cash on it if you can't afford it?
Tesla, and Musk, are risking everything by loosing focus and discipline. Even at SpaceX with their in-house satellite is goeing that way now. No idea why you would do that either.