Perhaps this is a sign that value in the stock market is largely disconnected from current value? it's entirely speculative. On the face of it, all it's saying

Perhaps this is a sign that value in the stock market is largely disconnected from current value? it's entirely speculative. On the face of it, all it's saying is that a lot of people believe that tesla will someday be the largest US carmaker ever. We can go even further than that though. People don't invest for the fun of it, they invest to make money. While Ford might have an awful lot of cars, owning a handful of shares is not going to make much money beyond predictable dividends and slightly above inflation year-on-year growth. There's not much room for future growth in Ford, so people are unlikely to ever buy shares at a high price.