Not everyone gets the Amazon shipping rates. Shipping is actually one of the toughest areas to try and compete in for a small ecommerce site, and it's probably the number one complaint received since people have come to expect free or extremely low cost shipping.
If using UPS/Fedex, you get the fuel surcharges, residential charges, and rural charges that can make a small profitable order become unprofitable (and cuts into profit margins of others). It can even be almost $10 to ship a 1-lb package in-state if to a rural area. And then you have to consider box cost, and void fill cost. I switched to USPS last year for 90% of my shipping, and it's still a loss at times from what I charge for shipping.