The Eink Carta generation (300dpi, 4-bit greyscale) has about 15Hz refresh rate when driven in 1bpp mode (black/white only). Combined with efficient partial refresh, this sounds like it'd not be more than a stylus sensor behind the display (as usual), and some software to properly translate this into partial refreshes.
The premium is not really high just from them having to spend particularly much. Either they make very nice margins on it, or it's really that expensive to get a screen that size.
> this sounds like it'd not be more than a stylus sensor behind the display (as usual)
And that would be a wrong guess. Eink readers with wacom styluses are not particularly new (e.g. Hanvon, onyx etc.). The remarkable 1's "claim to fame" was a greatly improved latency compared to these, i.e. to be much better than what you describe.
I tried one. And the screen did not seem any faster than the "EInk Carta" one in e.g. the Tolino Epos readers. I assume they fixed the issue with software being in the way of latency, and seem to make extensive use of partial refresh. And, yes, they did seem to integrate on a much lower level than any other recent consumer HID->screen drawing pipeline.
Back in the days of the C64, it was normal to have sub-frame average latency with +-0.5 frames jitter, due to low-level control that prevented artifacts when drawing directly to the framebuffer.
They have these but the contrast is so poor that it's hard to read for the resolution it claims to have. Try the mobile reader forums. There's large Chinese ebook readers.
