I doubt it's going to cost 500. I think at least 700!
I think because the screen resolution, and size looks like 2x Sony e-ink screens.
Plus they have to pay licensing fees to Adobe, Microsoft and other file format programs.
Then there's the thickness of the device, which also should host a wifi and sufficient powerful battery. out of the ordinary sized batteries will most likely cost more then standard ones.
the design of the case seems fully be made out of plastic, or fiberoptic.
Also their delay costs lots of money, paying the research and development.
Probably there where still issues with the controls; every review I read of the plastic logics reader seems to have issues with pageswapping.
I estimate the PR to be closer to 750,or perhaps even 800!