And readability. And only using power when making updates. Using a max of 2.5W instead of 100W is a big deal. You can now power a monitor from your laptop or phone.
Also, think about how things tend to work in the electronics industry. DVD players were $1000 in the 90s.
They dropped in price because they were being built and sold in huge volume; I don't really see that happening with this product. E-ink readers (and by extension screens) were very promising five years ago, but then the iPad and Android tablets came along and pretty much wiped that whole market out overnight, disregarding readability and power consumption because apparently that's not as strong a sales argument as people thought it would be.
I'd still like a screen like this though. I gathered I can convert my old Kindle to an external screen with some custom firmware, I might do that.
My conjecture: Kindle sales is part of a ecosystem sale, rather than standalone sale. There is definitely a segment for E-Ink display, but as a standalone desktop seller it might be hard.
Also, think about how things tend to work in the electronics industry. DVD players were $1000 in the 90s.