I agree -- I don't think that any kind of tunnel or tube approach can be done more cheaply than HSR. And I venture to predict that if it is a tunnel or tube co

I agree -- I don't think that any kind of tunnel or tube approach can be done more cheaply than HSR. And I venture to predict that if it is a tunnel or tube concept, it won't succeed in linking LA and SF. That said, if we take Musk at something close to face value, it has a major advantage that the HSR doesn't: it would be faster than the air route. That would give it at least a fighting chance to draw extremely high ridership and make up for high costs with high revenue. And if the idea is basically sound, but the implementation is impractical on the SF-LA corridor, then it could be put into use in some other intercity connection with more favorable terrain and lower land costs.