Before you say that it's ridiculous, consider how else $64 billion (current official estimated total construction cost of the project -- not counting operating cost)[0] could be spent:
- Commercial air travel costs around $0.10 per passenger-mile if you buy in bulk[1]. That means $64 billion could buy 640 billion passenger-miles of air travel. If allocated to the 11 million people who live in Los Angeles and San Francisco counties, the state could buy each resident 58,000 air miles of travel -- equivalent to about 88 round-trips between LAX and SFO.
- If the LAX-SFO air corridor becomes too busy, that $64 billion could also be spent upgrading existing fleets by buying 147 brand new A380s at an average list price of $435 million each. [2]
- If the environmental impact is a concern (not that laying tracks and punching holes through the Central Valley is free of impact), then buy new Teslas instead. Lots of them. At $35,000 per Model 3, you could buy 1.8 million new Teslas using that money. Add some solar panels to each purchase and you could still buy more than a million -- more than enough for every San Franciscan to get a brand new Tesla.
[0] https://www.mercurynews.com/2017/01/13/confidential-report-c...
[1] http://www.opshots.net/2015/04/aircraft-operating-series-air...
[2] http://www.airbus.com/content/dam/corporate-topics/publicati...
(Edit: added citation for $64 billion official estimate)