Important caveat: this is under Tesla's made-up accounting rubric. Under GAAP accounting (i.e., the standardized accounting methods everyone else uses) they lose money on each car, i.e., they have a negative gross margin.
1) Tesla's GAAP gross margin was 14.5% for the most recent quarter [https://ir.tesla.com/static-files/1e70a30c-20a7-48b3-a1f6-69...]
2) Breaking out GAAP and non-GAAP figures is totally standard and commonplace among publicly traded companies. Take a look at Ford's Q2 letter, for example, which includes a whole page describing how and why they use Non-GAAP financial measures to supplement GAAP figures [https://s22.q4cdn.com/857684434/files/doc_financials/2019/q2...]
I'm not rooting against or for Tesla, but they are extra shady regarding accounting. They are losing money on each car. There is so much misinformation around this pushed by Tesla fans and the company itself though that you might easily believe they are profitable, but they are not!