LIFETIME warranty? That would make the device cost a heck of a lot more than $400 right there. I would like a lifetime guarantee of access to my content (if they stop supporting it they have to provide a transition path) but I don't think it's reasonable to expect that $400 entitles you to a lifetime of hardware. TVs are several times that and people expect they'll stop working eventually, too. If $400 is too much for you to consider the device at this point then it's probably not the time for you to make the move. As time goes on, the eink screen prices will go down. Right now that's about half the hardware price right there. People assume Amazon is price gouging because the price is higher than they want to pay. I doubt there's much profit on this thing at all. If you consider the three years of R&D it's selling at a loss and they're hoping content will make up the difference. It's a new market and the early adopter types that are OK with shelling out $400 for a new and interesting technology are the ones that are participating. People who want low prices have to wait for the technology to mature.
Remember how expensive LCD monitors used to be? Now practically everyone has them. The last one I bought would have cost me four times as much had I bought it a few years ago. When the price gets to your comfort point, then I say go for it. The devices will be even better then, too. The way things move these days, I doubt it will even be that long. I hate waiting, too.