you have to also remember that AMZN is now getting "present value" increases in its' other business: e-books, cloud computing,and I guess, the shipping part now. It's a rollup of more than physical internet retailor.
Except what they did with shipping reduced their expenses. More than physical? How is relying on UPS's or FDX's physical assets any different? You just pay more to a middle man. I can see you do not have much of a head for business. You would rather pay more to a third party than pay less by foregoing them in order to claim you aren't reliant on your own physical assets.