Are there any e-ink displays with a reasonable enough refresh rate that aren't exorbitantly expensive? I know atleast as of a few years ago that was one of the issues that would've impeded an e-ink only laptop

I feel like e-ink displays/EPDs are widely used, but underexplored, by major manufacturers at least. The person behind the Modos project already linked by someone else has put a lot of effort into pushing EPDs to their limits and put together the best technical documentation for EPDs that I know of: https://github.com/Modos-Labs/Glider

EDIT: Here's an older demo of theirs: https://www.youtube.com/watch?v=XduK7wn9SE4

From what I read some time ago, e-ink displays use almost as much energy as normal displays if the contents change all the time. The one benefit of e-ink is the ability to show static content without using energy.