Amazon is valued based on the implicit assumption that Bezos is a Buffet tier investing genius. So far, that assumption has held. The main difference is that Bezos invents new businesses in addition to buying them. Nobody is arguing that retail isn't a big part of their business, but it was only ever meant to be the bootstrap. It's incredibly rare to see such executive and entrepreneurial skill combined in the same individual.

Yes, this is my take on it as well. They're betting he can keep growing at 20% for many years to come, which would be almost unprecedented for a company of that size and age.