There is a new study from Consumer Intelligence Research Partners is saying that users who own a Kindle Fire tablet spend an average of $1,233 through Amazon per year; and, those who don't own a Kindle Fire average spending of just $790 per year. Now, there will be those who claim that the $443 difference between those two numbers nullifies any potential revenue loss on hardware. But, we would point out that those numbers point to total purchases, and Amazon doesn't get that entire $443 in revenue, not even close really.
Amazon has been running at the same 30% cut that you'll find with Apple's iTunes or Google Play, so even if all of that revenue came from apps, games, movies, music, and books, that would mean just $133 in revenue for Amazon. Of course, if that revenue comes from something in the general Amazon store, the cut is far less than 30%.
Even so, over the course of a device's lifetime, that extra revenue would certainly make up for any shortfalls on hardware. The question is whether or not this extra revenue would hold when shifting to an Amazon smartphone or not.