I suppose so. But they're still charging 10x what I pay per MB for my cellphone. I use Ting, which runs on the same Sprint network as Whispernet, and I get 4G.
Amazon Whispernet works in most countries (even down in southern africa) and allows multiple re-downloads of the same book. Most people probably don't download a book ten times, but twice is fairly common for me (multiple readers). Comparing the price with the raw bandwidth price on a single network is not a fair comparison.