It's a great question. Future potential, leadership, tech stack, manufacturing capacity, etc. There is a lot of "soft" aspects of running a company and valuation is one of the most difficult/error-prone things to do.

Damodaran's Google talk kind of does a good job describing valuation of high-growth companies (it is deceivingly simple): https://www.youtube.com/watch?v=Z5chrxMuBoo