Do we need the middle class?

Kevin Drum writes that

One way or another, there’s really no way for the economy to grow strongly and consistently unless middle-class consumers spend more, and they can’t spend more unless they make more.

This is a widely held view, and I’m as much in favor of a strong middle class as anyone. Nonetheless, I’d say that in terms of strict economics it’s wrong. There’s no obvious reason why consumer demand can’t be sustained by the spending of the upper class — $200 dinners and luxury hotels create jobs, the same way that fast food dinners and Motel 6s do. In fact, the prosperity of New York City in the last decade — largely supported off of super-salaried Wall Street types — is a demonstration that you can have an economy sustained by the big spending of the few rather than the modest spending of large numbers of people.

I DON'T AGREE WITH PAUL,beacause of OPPORTUNITY COST!