If you're running a company that requires 5-6 interns, at what point do you decide to, I don't know, make money?

The fallacy that you have to build to enormous proportions before you make a penny in profit seems only to exist in SV. That's why people question it. The vast majority of business elsewhere try to make money ASAP. Some of them even grow quite large.

The idea is that some business models are more capital intensive than others to implement (like establishing a two-sided market place or building something tangible like electric cars).

Yup. The company I'm was was self sufficient after its first few years. Grew slowly and organically. Funding has only been to speed up that growth once our products were proven.