Aside from iRex, which has its own e-ink factory (which seems to be serving only iRex's requirements), everybody is buying e-ink from a single source: PVI. As far as I know, they're the only ones currently licensed by E-Ink Inc. to make the stuff.
Part of the high prices on e-ink devices is likely the still limited manufacturing capacity. But I suspect that part of it also stems from the fact that (unless you're iRex) you can only get the stuff from one place.
