Even in the 10s of thousands, these price differences should probably be a secondary issue for many commercial contexts... at least at the startup end of the game.

If you are producing a $40 microwave, smart bulb or somesuch... shaving dollars off component costs is operative. I think this supports your original point rather than detracts from it. This is the mass production game, a mostly big company game.

Microcontrollers have reached a cost point where the dynamic has inverted. The people who need to care about a new, cheaper-than-ever mc are large companies, not startups, hobbyists and niche product designers. There will be lots of exceptions, especially hobbyist use case... but generally.

There is such a thing as cheap enough.