I have a Boyue Likebook Ares - it cost £190. https://shkspr.mobi/blog/2019/11/gadget-review-boyue-likeboo...

It has an 8inch screen - about the same size as the iPad mini. It runs Android 8 but, obviously, some apps work better than others. It came with several nibs for its pencil.

They have an 10 inch version for around £230. See https://goodereader.com/blog/electronic-readers/boyue-p10-is...

So, there are some cheapish, largeish, eInk devices out there.

I was told (and I have no way to back it up) that the yields on eInk are fairly low. They make a couple of square metres of screen, and then have to cut it to size. Because of defects in the process, they can have a lot of wastage. So the larger sizes are disproportionally more expensive.