> Why can't Pine64 make $400 pinebook pros?

Money: Pine64 is a small operation with limited resources, factories have minimum order quantities among other commitments.

Most Pine64 products have pre-alpha software and are aimed at volunteers who can improve it. Lots of people are willing to buy a product for <$150 and "see how it goes". $400 filters out a lot of people who might otherwise chip-away at software bugs on weekends. Additionally, people are less tolerant of dead pixels on a $400 laptop, and Pine64 would rather not deal with returns.

The reason I've seen for the phone hardware is that they simply can't source hardware that is more performant but still open enough to sufficiently develop for.

Probably because then most potential buyers would be purchasing low-end windows laptops, I guess.