Well the pricest component is the screen, and that's under patent.

I think rising consumer expectations soak up a lot of that -- you could make the main board and other components a third the price if you're satisfied with mid-2000s specs e.g. 200MB storage, slow page turns, bundled radios, no touchscreen, no PDF support, etc.

At some point the raw materials cost (which generally aren't getting much cheaper) becomes a major factor and that's harder to cut without a new approach.

Eink screen aside, it may be that we're just nearing the limits with current manufacturing approaches and that the next leap requires a wildly different approach.