Does having Tesla as a customer make Dell stock a buy?With a valuation more than 6 times sales, Tesla (TSLA 0.49%) costs significantly more than rival automotive stocks like Ford and General Motors, both of which sell for mere fractions of 1 times sales. Tesla fans defend Tesla's high valuation, arguing Tesla is more than just a car company -- that its investments in artificial intelligence to power its self-driving car technology mean Tesla is really an AI company.And investors in Dell Technologies (DELL - ...