> If batteries reduce the demand for oil

That's a big IF.

Also, it ignores the fact that every car manufacturer already has a plethora of fully electric, or hybrid models available (and they are, on average, far cheaper than the cheapest base model Tesla can offer), and the markets still don't buy them.

This also ignores the fact that many companies make great batteries, and Tesla is only recently sitting down to that table. Why wouldn't Panasonic be that "trillion dollar" company? Or Sony? Or Fujitsu?

Put a probability on the IF and multiply it by the revenue of the oil companies and you've got a valuation for Tesla.