I started watching the video linked at the top and the first anecdote is about Elon Musk using first principles to determine he could be rockets cheaper than current companies. He compared $130m to the price of raw materials of a rocket at $2m. But isn’t that comparing apples to oranges? And the exact thing that would get you in trouble when doing back-of-the-napkin estimates. That is, $130m is how much rocket companies at the time were _charging_ NASA for rockets, not how much it actual cost those companies to build.