Well, that would require more than a little bit of 'hacking' -
In fact, it would be a fairly major engineering challenge (the display interface is different on e-ink screens than other screen types).
A better approach would be to have a manufacturer of a modern 10 inch tablet, "re-screen" the in-production device.
But for a one-of-a-kind device, your estimate is a few orders of magnitude low.
So, how to make (no pun intended) it a non-one-of-a-kind device?
Do you have contact with a community of people with similar vision problems?
If not, see if you can find one through you medical care contacts.
If large enough group, then you might stand a chance of "selling" the idea to a manufacturer;
Otherwise, with a smaller group of interested people, you might be able to form a "kickstarter" project to just hire the building of the specialized tablet.
PM me if interested in getting an e-ink tablet produced (I don't make 'em, but I know a few people who do).