I wonder if there's a non-margin factor in play. Maybe something like:
* They don't want to be in the "support" business, so by keeping the product line away from hobbyists/small players, they keep their overhead low.
* Their main concern is product secrecy and therefore will only deal with firms large enough to take NDAs and licenses seriously
* Their manufacturing capacity is finite and not easily scaled, so they couldn't actually deliver on a hypothetical millions-of-screens-per-year order.
* Some sort of brand protectionism. I see a lot of "we could probably hack and rig an E-ink display to do something outside its normal sales case" discussion. I could imagine a situation where they ended up-- in the eyes of end consumers-- responsible for the failings of such products. They never said to use their panel as a desktop monitor for playing 60fps video, but they can't stop someone from trying and then bellyaching about it to the world.
Of course, a mandatory-licensing mechanism could help escape whatever tarpit they're in.
Again, I think it's...rather a lot of hubris to assume that a company is doing the less profitable thing (and it is an assumption, since none of us have better data than they do).
That said, sure, we can speculate there may be other factors at play.
If you're saying that even holding a monopoly, the most profitable price point is at market saturation, I'd need to see something backing that. And also what you mean by market saturation; the cost of parts for an iPhone 11 Pro is estimated to be ~$490. The list price is, what, $1100? You're basically saying that either they've already achieved market saturation, and would gain no new customers dropping the price to $600 (parts + $100 for distribution, assembly, etc), or that they're leaving money on the table. I find both of those very hard to believe. So maybe I'm misunderstanding you?