This is fairly well-written, but I disagree with two points. a) You might not know what you normally pay for groceries but I think most Americans have a rough

This is fairly well-written, but I disagree with two points. a) You might not know what you normally pay for groceries but I think most Americans have a rough sense of what they should pay for their items. Even if they don't know, it will eventually become easy to find out what the market price is (e.g. Google probably will have this). b) Amazon's retail business can sustain higher margins than Costco because it can sell non-popular items. I agree that mainstream consumer retail items are sold at extremely low margins. But if you want to buy something more specific, the margins go up because your options to buy this item become limited. This is a large reason of why AMZN worked so hard to develop a reputation as the "everything store"