People, leave your comfort zone. USPS has been delivering Amazon for quite some time.
Amazon and other retailers, use the scheme of "free shipping", which is embedded in the price no matter what.
I used to sell on Ebay, say an $8 item, they would buy 3 of them, I had to deduct some $ from my shipping charges to make them happy. I would end up paying $10 in shipping for the items. $14 profit. Now, my items are free shipping, they just don't know they used to pay for it.