Is McDonald's really worth $100 billion?? It's some guys making hamburgers!

Valuation is based on a whole host of things including revenue, brand recognition, distribution, customer acquisition costs, customer retention rates, switching costs, growth, etc. You could start a Dropbox competitor and have none of those. The business matters far more in valuing the company than how hard it is to replicate the product. It's much easier to make a hamburger as well as McDonald's than it is to make a business as good as theirs.