"That, by the way, is roughly how Amazon.com sells you books for so little" What? You mean Amazon makes some sort of "margin" off the sales they make? How does

"That, by the way, is roughly how Amazon.com sells you books for so little" What? You mean Amazon makes some sort of "margin" off the sales they make? How does that system work? I thought they'd make money selling google ads. I thought they pay the cover price and then get a little from the shipping