I think another key thing is in three years the price of storage will keep falling (as it has over the last X years), and with Amazon they are eating that cost

I think another key thing is in three years the price of storage will keep falling (as it has over the last X years), and with Amazon they are eating that cost (hopefully) and not sticking you with old outdated hardware. Kind of like leasing a car, but the cars get 10x better every year