I would guess there's not enough volume due to limited use-cases of the tech compared to more traditional screens.

The typical e-ink uses cases boil down to e-readers, dumb-phones, and hobbyists, which is not a huge market. Anything niche or specialized tends to carry a higher cost.

It's cheap if you are buying the small displays they use at supermarkets. No business is buying these massive displays.

The prices on Ali Express for e-ink are not that bad, but certainly can't get anything as big as the Mira Pro. The Boox premium is plug and play compatibility, high fidelity/refresh rate and support.

Patents