At the moment, all the analysis I've seen points more towards the only reason it's cheaper being because of the smaller size of the tunnel (there's actually nothing novel about the boring machine, it's just a standard one that is used to build utility tunnels with some minor tweaks), and because they don't build (or don't take into account) things like station caverns, cross linking tunnels, ventilation/emergency egress, etc.

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.

It's not exactly the same thing. In the Boring underground car-train, each party of travelers takes up an entire car's or truck's worth of space. On a subway, each person takes up room for themselves and their belongings. Plus maybe a bicycle. You can move a lot more people at once in a subway.

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.

This article that we're discussing, about Las Vegas, involves dedicated vehicles, not personal cars. And one of them is a 16-person people mover. It is expected to have a low enough usage that that makes sense.

How many people are you expecting to take their bikes on the subway on the Vegas strip?

But it's not gonna be "for much less" because digging tunnels is probably the easiest and cheapest part of building a subway.

Subway cost in mismanged US are ridiculous.[0] Around the world, countries like Spain are already building tunnels for the claimed cost of an Hyperloop tunnel.

[0] https://pedestrianobservations.com/2019/03/03/why-american-c...