They are quite sensitive to the prices of things they buy regularly, but not as sensitive to the prices of things they buy rarely -- unless they are relatively expensive.

Otherwise, price is only one factor. You also have to consider delivery times, convenience, support and other factors. I buy things from Amazon partly because I can reliably get them the next day, and they'll take them back if there's a problem, even if it's my mistake.

> there's no money in delivering groceries to people. Groceries are notoriously low-margin, one of the lowest margin businesses there is, so delivering groceries to people doesn't seem like it's going to make Amazon the trillion-dollar company some people think it will eventually become.

I agree about groceries. It's going to be particularly tough in areas where major supermarkets are already delivering groceries, which they do where I live.