From a glance at wikipedia, Tesla took 5 years (2003 to 2008) from founding to (limited) production of the Roadster, and were under no expectation to get money

From a glance at wikipedia, Tesla took 5 years (2003 to 2008) from founding to (limited) production of the Roadster, and were under no expectation to get money or build other cars during that time. Then they built what appears to be a total of 2400 of them. The Model S was announced in 2012 as their first "mass produced" road car (and they don't appear to have broken 100K cars in a year until ~2017), so that's 15 years to get anywhere near the scale of a grown-up car manufacturer. To reiterate, they didn't have to support other production in any of that time, and they didn't have to make any sort of profit during any of that time. To compare, Audi spits out ~2m cars a year, and can't just stop selling cars to retool their factories.