What are some cheap 8-10 inch displays?
I've wanted to do research on this a few years ago too. At the time development kits including 2 displays cost up to 5000 dollar.  

If you can live with a bit smaller dimensions your cheapest option may be to cannibalize a Kindle. Six inch for only 79 dollar.
I own one and it has excellent resolution, under a jeweller's magnifier it looks like paper.  

Color e-ink displays are not common yet, and may be prohibitively expensive. I would stick to grayscale.