From my seat, that really remains to be seen. The existing companies don't seem to have found a way to compete with Tesla's EVs yet. They may get there eventually, but Tesla has it now.
Regarding valuation, one point I read elsewhere is that Tesla does a lot more in-house, which adds to the valuation, whereas the existing companies will buy a lot of their parts and/or contract out work. I don't have a source on the specifics, but if true, the logic certainly seems reasonable and would explain things. The value of a company shouldn't be based on their final product, but on the value they added to the parts/components they took in to create that product.