I think this is bullshit. Uber may be worth more than auto makers, but this is a bubble and will not last (unless uber manages to create an autonomous taxi service in the next few years). They were just lucky and intelligent enough to get around regulations, but regulations are catching them.
Uber's tech is simple and easily replicable. The moment they raise their prices, they loose their market share. There is no network effect in this market.
It is simply obvious that Uber provides much less added value than any automaker.