Some LLM-assisted guesstimating tells me that in terms of raw cost of manufacturing and delivery, given an average (non-voracious) rate of consumption, supplying paper books is still several times cheaper than supplying usable E-Ink devices in non-price-rigged markets.

Supplying kids textbooks in India in paperback, for instance, is at least 5-6x cheaper than supplying them the same in an E-Ink reader despite the ginormous (10-12x assuming 6-7 books each year) difference in freight volume.