That Barron's article is awfully written and poorly explained, but there is a nugget of truth in there.
The article misses the brand value. I'm short, but even I will admit that driving a Model S is an awesome experience. There's real, but intangible value there.
Even if Tesla were valued like a traditional automaker, its brand would still justify a best-in-class valuation.
The trouble is valuing the future of the automaker industry. The industry will have a huge shift in the value chain with the creation of Level 4 autonomous vehicles. And I really believe Google/Waymo is going to dominate the autonomous vehicles war.
The reason is Google's talent and access to capital. They are really ****ing good at bleeding edge AI and Machine Learning. Tesla might have a long-term data advantage (and I stress might), but they don't have the talent advantage, and Google is getting close. They're doing amazing stuff with Google Assistant, Google News, medical imaging, etc.
Credit to GM/Cruise though. They're promising a car without a steering wheel in 2019.
Google does match Tesla's data collection. Part of how Google is overcoming their lack of data is by outright purchasing car feeds. They then use Recaptcha to train their object recognition models (ever been asked "which of these contains a stop sign?"). Android phones and Google maps users give it road and traffic data.
All of that does introduce one hilarious risk unique to Google: monopoly risk.
Regardless, whoever wins the race to scalable Level 4 autonomous driving will be on the brink of an incredible, world-changing opportunity. I don't think it will be Tesla.
Without that, the question of how you value "traditional automakers" goes away, because the value chain is massively disrupted.