Just a guess... I think I read somewhere on MR that the e-ink screen runs about $90. If that's the case, I just consider my jetBook purchase compared to the competition (at the time) as such:
jetBook: $170 (NewEgg)
Sony PRS-505: $260 (various)
$90 difference!
BTW, not even Ectaco sells it for $300 straight on their site. They run various promotions such as discounted prices and extra accessories (earlight). In fact, "TODAY ONLY!" you can get it for $250 with the light. Or then there is their offer of "Don't want to pay $300? Name what you will pay and we'll consider it!" (Bid your price!)
IMO $199 is more reasonable, or with current 5" competition, $150-$175.