Quite honestly, what's going on here is probably just experimentation with the new medium. It's all a question of demand. If the convenience of reading it on the Kindle is actually viewed as a commodity, and people will pay more for it, then more will be charged, it's simple economics.
I personally think that cheaper books is the selling point, not easier-to-read books, and that they'll come around eventually.
In any case, S&S is at least playing with the format; the Star Wars people are all but ignoring it entirely, only releasing completed series well after they've finished.