Google's tablet business model is actually superior to
Amazon's. Google has better ad. monetization than Amazon, and just as good a theoretical monetization of digital media (movies, music, and books).
Amazon has sustainable advantages in a shitty business (retailing/warehousing/shipping physical goods) but when it comes to digital media, it's just bits, a commodity. It is much easier for Google to sell digital content than it is for Amazon to monetize web browsing and email, which is what most people do with tablets.