Earlier quoted context omitted.
You can scale with tunnels. I also suggested congestion pricing in my last paragraph. Having congestion pricing on highways is also a good idea because it can reveal the price people are willing to pay for uncongested travel. That gives people an idea on how much a tunnel could make and motivate spending money on building it.
Tunnels right now are way too expensive per lane mile. And you also need interchanges to connect surface with tunnels, which runs into the same space issues that exist above ground. Yes, the Boring Company is suggesting we can somehow solve this expensive tunnel problem with sleds for cars and vertical elevators, but those are all proof of concepts, and in any case they would probably be less reliable than current in…
You could just do this by walking and elevators, but more extensive transportation would give even more options. There should be 10 or 100 or a 1000 Boring Companies working on the problem with transportation in cities. It is one of the 5 or 10 biggest problems of our age.