The overbuilt body is most likely due to two factors: (i) Tesla does not have the design know-how to do better (ii) Tesla's manufacturing capability is below th

The overbuilt body is most likely due to two factors: (i) Tesla does not have the design know-how to do better (ii) Tesla's manufacturing capability is below that of other car makers. As I've recently outlined in another comment, the manufacturing process for these is quite involved and finely tuned. People who do (i) also don't grow on trees, because self-supporting car bodies are basically the pinnacle of that particular engineering discipline; essentially no one outside that industry has a need for those requirements in that combination and manifestation.