Company executives are often smart, and often know their business better than anyone else, but they're also biased. What comes out of a CEO's mouth is very like

Company executives are often smart, and often know their business better than anyone else, but they're also biased. What comes out of a CEO's mouth is very likely to have more to do with what he or she wants _you_ to think than with what _they_ actually think. So taking CEO's grand theories with a grain of salt is in general a good idea for investors. As to why margins matter... Bezos' quote talks about how valuations are multiples of cash flows. This is true, but multiples aren't constants. Basic investment theory suggests that the multiple should be an increasing function of the company's growth rate, its ratio of sales to assets, and its margins. So if you want to maximize your company's value you ought to be concerned with all of those things. Which isn't to say that trading lower margins for higher growth is a bad decision in Amazon's case, but it's not like it's an irrelevant number.