[darwinwhy]

Have you looked up small, light items on Amazon and seen that they pack them up packs of large N? They do that to hide the fact that delivery is actually a very large fraction of cost on such items. Food delivery, as mentioned in the OP, is another example.

[Cerium]

Exactly - rule of thumb is that about $4 of any small item on Amazon goes to Amazon. That seven dollar cable is really at best a $3 cable, including costs to get the item to Amazon in the first place.