[j_s]

Not sure how specific you're trying to be - here's a specific example of 4.2" at $35. I actually would be interested to see a graph of cost-per-square-inch to see where the arms and legs actually do come into play.

https://www.aliexpress.com/item/400x300-4-2inch-E-Ink-displa...

https://news.ycombinator.com/item?id=15721766