These "how much will it cost them" analysis reports are always kinda stupid, in my opinion. We have no idea what Amazon's actual cost to assemble is, shipping to their fulfilment centers, what the cost to support the device is (like the EC2 servers powering silk), how much engineering went in, both hardware and software, what the support costs will be....
It might give a baseline for "what do the components cost", but even if the components cost $150 and they sell it for $200, its still very possible that they actually lose money on the device itself and need to recoup via digital services sold.