I think Tesla bulls and bears are talking past each other.
Please note that the bull case is not ludicrous:
1. TSLA is at a competitive advantage over it's electric car peers.
2. There is a good probability that TSLA will gain competitive advantage in the entire car market sometime in the next decade. If you question this, consider that this is just a 2X price improvement away and that almost always happens in a new technology.
3. Once #2 happens + new technological advances like self driving, entire new market sectors get created out of thin air. There is no current market area where to capture this valuation.
4. This is likely just a jumping point for Musk to other, much more consequential industries. IF total ownership cost of grid-scale batteries go down by another 10X to 20X with Tesla at the driver's seat, then the entire energy sector becomes it's oyster.
If all of these go according to the plan the bulls have set, the TSLA should indeed be much more valuable than even AAPL, and not one-eighth of it's market cap.
While the above position is not ludicrous, I think it is underestimating the risks associated with each such step. Musk has shows that he is able to take huge risks and somehow can use his star power to avert disasters. Each step in this process would involve huge capital allocation, and a risk that either an upstart upstages TSLA at innovation or someone like AAPL just outspends them to that competitive edge. Remember the cash crunch Musk had a couple of years ago? These crunches will keep coming for the next 15 years for Musk to keep this trajectory going, a necessity to justify the bull case.
Betting on a specific player to be able to continually innovate is a risky one. Doubly so when such innovation will always require massive piles of cash to be sacrificed at all stages.
Because of this TSLA is really a binary case. If you believe that Musk will keep the same trajectory going for another 20 years, then it is worth a whole lot more than even it's current stock price. If not, it will likely not be worth any more than a tenth or twentieth of it's current price.
I, personally don't do such investments. But I can see particularly bold (but rational) investors betting their play money on such speculative moonshot investments.