Competitive pricing
Menezes at Gartner speculates that the phone could be offered on different price tiers. One tier could be a one-time payment for the phone that offers Amazon's apps and services but a limited number of other features. A higher price tier could feature a monthly bill and a phone with more bells and whistles.
It's difficult to be competitive on price in the cutthroat phone market. But as Amazon has shown with its tablets, the company is willing to deliver high-quality hardware at a loss in order to undercut competitors like Apple and put its devices in the hands of people who will use them to buy Amazon's goods and services.