[dcotton]

I still compare prices when I'm about to buy something from Amazon and they are almost always the cheapest still. That's even before considering the 5% rewards the amazon credit card gives me. Maybe you are seeing certain types of merchandise that went up there? Or my purchase habits just happen to line up with their pricing more than yours.

[jjeaff]

The laws of economics are unbreakable. You have to realize that someone is paying for the shipping and that someone is always the customers. Or at least temporarily, investors.

[21]

But another very strong law of economics is that scale reduces costs.

[thaumasiotes]

There are other economic principles that apply to shipping specifically. It's a pretty old field.

A last-mile delivery truck goes out full and comes back empty. That's terrible logistics, but the fact that it happens anyway suggests that shipping from your home to a UPS center should be basically free - the marginal cost is nearly 0.

Amazon returns have to go through UPS. If Amazon sends out a lot more stuff through UPS than it receives from UPS, returns might just genuinely be free, occupying what would otherwise be slack in the system.