Even then - your statement is simplistic - the future cashflows are discounted back to today. As an example, if their revenue is $1 trillion (assume no inflation for simplicity) in 50 years, and we assume 10% net income margin (probably in the ballpark of reasonable) they make $100 bill which is discounted 50 years to today at maybe 8% (?), that year's earnings is worth around $2 billion today.

You may reasonably counter that they will grow much faster than that - and this is where people (like me) question it. The total industry is ~$3 trillion or so, globally. 85 million units. Telsa will hit maybe 900k units this year. So its a tough sell that they'll get to 25-30 mill units anytime soon (from a demand or supply side).

Don't get me wrong - Tesla is brilliant, Elon is brilliant. It doesn't mean the company is worth infinity. There is some concrete number which makes sense... and to many folks, 1 trillion is an order of magnitude too high.