Compaing US sales of Model S for 2015 to say something like a Toyota RAV4 (a popular but not top selling car in the US)

https://en.wikipedia.org/wiki/Tesla_Model_S#Top_selling_coun...

https://en.wikipedia.org/wiki/Toyota_RAV4

Model S 2015: 25,202

Toyota RAV 4 2015: 315,412

In the US, the best selling vehicle the Ford F-Series which sold 780,354 in 2015

So I wouldn't say it's not mass produced, but it hasn't hit full economy of scale, and isn't designed to.