Selling at a loss is a real thing that lots of companies do and is entirely possible in Tesla's case. By this I explicitly mean the marginal cost ... that is the sale price may well be lower than the cost to make one more vehicle.
They would do this strategically to build their brand, market share, to work on inefficiencies in their pipelines expecting to make it up further down the road.
>Selling at a loss is a real thing that lots of companies do
Except products sold at a lost are almost always loss leaders designed to increase other revenue sources. It is fine to sell razors, printers, or game consoles at a loss if products like blades, ink, and games sell for a large premium. The problem is that Tesla doesn't have any other products to offer. They sell cars. You can't really expect to function in the medium to long term as a business if your only product sells for a loss.
There is a big difference between not being profitable as a business by either reinvesting revenue or using loss leaders to grow market share and losing money on every single product you sell.
It's been part of Tesla's business model to progressively build cheaper products in progressively larger quantities.
Also, Tesla is still building the world's largest battery factory. "Reinvesting revenue into capital improvements" seems to parallel Amazon's early-2000s growth fairly well.
They would do this strategically to build their brand, market share, to work on inefficiencies in their pipelines expecting to make it up further down the road.