Seems like only pure software businesses (which are extremely capital light and often come with network or lock in effects) can justify the really crazy valuations.
Hell, even robotaxis will have price pressure if market affords say 3 or 4 players. Not many will pay double compared to competition.
Which also happens to be where most of the money would be, so it's probably a good bet. Tesla seems to be hoping to displace Uber in the suburbs, while being an also-ran against Waymo in the denser downtowns. That includes ferrying a fair number of people into and out of cities, where Waymo can't (currently) go.
That's probably not as lucrative as Waymo's core market, but it could have some decent margins.