GM has higher operating margin than Tesla by a substantial number, and is expanding into electric cars.
Running at a loss to build out market share, technology, branding and economies-of-scale is a standard startup strategy. Tesla is still in that stage.
The key question is whether things like the Gigafactory provide Tesla with unique economics and competitive advantage. If they do, Tesla will be able to have lower costs or more expensive products than GM. If not, it's overvalued.
That's just GM. Ford and others are the same. The Ford F truck line is practically a money printing operation.
A fancy UI on a screen is not a defensible moat, not when you suck at manufacturing (QA is still bush league).