With all due respect to @Paraclesus, your use of that expression is so trite, it's meaningless. Elon used it in the context of applying physical science to natural phenomena. Your repeating it in a financial context illustrates a challenge in original self-expression.
I did not reason to anything. The OP pulled a key financial metric (operating profit margin) out of whole air. I tested the plausibility of the value he asserted by using the most recently available financial information and projecting it forward. What "first principles" are you using to estimate 2018 operating profit margin and what percentage does your "reasoning from first principles" inform?
Since you lecture others to keep a copy of the 10Q on the nightstand, do you even realize that only $5.2 million of the $213.9 million in reported 1Q17 Energy Generation and Storage Revenue was attributable to Tesla Energy? All the rest was from SCTY's run-off. How much additional revenue in 2018 for TE does your "reasoning from first principles" inform?
Here's what Elon predicted in a Conference Call from two years ago this week:
"Yeah. I do want to preface this with some degree of uncertainty, because this is quite new, and again, we've got that challenge of exponential ramp and then depending upon how you move the – on how the dates fit over an exponential ramp, the actual numbers in a given quarter could be quite different, but the demand has been really crazy, so it's well in excess of – I mean if you just take the reservations that have been made thus far, it's well over $1 billion worth of Powerpacks and Powerwalls. So – and that's with no marketing, no advertising, no sales force to speak of, really, we're not trying to sell it, it's basically a presentation and a webcast and 30 minutes of press Q&A.
So there's probably room to improve. So this is – I mean, really, we're basically sold out of what we could make in 2016 at this point. And assuming these orders are real, which they seem to be. So were looking at maybe, again, just to preface with meaningful uncertainty, $40 million to $45 million in stationary storage in Q4 and maybe as much as 10 times that number in for next year. [i.e 2016] So it's $40 million to $50 million that this year and 10x of that next year. And I mean that growth rate is probably going to just, keep going at quite a nutty level. It's probably at least a few billion dollars in 2017, somewhat speculative at this point, but I think that's likely. So it's sort of growing by half order of magnitude to an order of magnitude per year."
That "management guidance" has validity equivalent to "100,000 to 200,000 M3 deliveries in 2H17." (and "verbal approval").
Unless mandated by governmental decrees and perceived emergencies (like Aliso Canyon and South Australia), market based energy storage projects have a lengthy gestation and execution period, viz. the Kauai project which was awarded in 3Q15 and those 52 MWhs will first appear in the Operating Statement for 2Q17.
You are misrepresenting that the bolding was a challenge to his revenue estimate as "too optimistic." It was not; it was to contrast his estimate for the growth in Revenue to what could happen to the growth in OpEX. IMO, his Revenue estimate is plausible if Tesla executes well. I challenged his operating profit margin as "too optimistic."