Tesla is impossible to value

Sure, and the poster boy for this is Amazon. But if in 1998 Walmart executives had had the insight to recognize that a competitor with much lower costs (just like themselves previously) would be worth competing with directly, well Amazon wouldn't have been the stellar investment it's been.

Will Tesla be as lucky with clueless competitors? Unlikely but, nevertheless will Tesla justify it's current valuation? Probably. Hedging on Musk's continued unabated abilities would be a good idea.

I value them at far higher than the market does. See? Not impossible. My valuation comes from intuiting that they will succeed and go on to selling 5M vehicles a year, with industry leading margins because of the embedded software premiums and supply/demand imbalance. Also they have a decent probability at getting a large chunk of the TaaS economy which itself looks inevitable and worth trillions. But yeah, if you want to use 2017 P/E, good luck.

Then stop trying... let them prove or disprove themselves and we'll go from there.