These days, it is standard practice to sell a printer for nothing but then sell printer ink so as to make a profit. Same as with razor blades. But tablets are much more complex then that model can accommodate. In this analogy, content is the razor blade or ink. Anyone can make a razor blade or ink, but content is much harder to come by. Not many can truly offer it. One reason why apple is successful is because they developed that business long ago. Same with amazon. Few others can play in this game. Sony already got out.
I bought a low cost google tablet but they will never get a dime on content from me. Many who buy a low cost google device will be the same way, too. Amazon has a chance, though, because they are king of customer service (I buy content from them, but I don't like their tablets) and content. Google has no idea of how to treat a customer, or at least, not a consumer. The winners in this whole space will likely be determined by who has deep enough pockets to survive through until the end of the bottom feeding.