If I were to buy the author's book and download it to my non-3G Kindle over my own wi-fi connection, the author would still be charged $2.85 for it.

Surely the 3G Kindle owners should be paying for it - and only then if they use whispernet. Or rather, I always thought they were because the 3G Kindle touch is $50 more expensive. A cellular radio only costs a dollar or two, I always figured that most of the $50 price difference represented average download costs over the expected lifetime.