Further, when the Boring underground car-train "stops", and parties leave the train, those cars still demand that same space, just on the surface. With mass transit carrying pedestrians and cyclists, you need much less room on "integrate" passengers coming out from the underground, with local traffic on the surface.
If Boring gives up on the personal vehicle folly, and can build a smaller, cheaper, but equally safe tunnel for mass transit, great. But they seem preoccupied with letting people keep their cars.
How many people are you expecting to take their bikes on the subway on the Vegas strip?
[0] https://pedestrianobservations.com/2019/03/03/why-american-c...
So if they actually built a subway it would cost... about the same as a subway. That's not to say that US subways aren't crazy expensive to build compared to Europe, Asia etc. - but that's more to do with legal issues (industrial relations etc.), business structures, and possibly corruption, rather than the technology.
If they can somehow address the insane tunneling infrastructure costs in the US, I don't really care what path they take to get there.
You could maybe save on OSHA concerns if you can somehow slash the number of people employed, but you'd need to get rid of a LOT of people before you see enough gains from that to make this a game changer.
Elon's whole deal around transit is utterly uninformed about anything urban planning.
Experts (including those who have studied foreign mass transit in detail) are at a loss to fully explain why the US's tunneling costs are so out of whack compared to other countries. Sometimes, when expert systems seem to have failed, it's a useful exercise to throw everything out (i.e. be "utterly uninformed") and learn from scratch by trying. They may fail anyway, but it's worth a shot.
Sometimes, the naive intern will find a solution because of their own naïveté. (And even then there are lots of practical things that will need to be relearned, at great pain.)