As I've written previously, the cost estimate for this entire project was about $77 billion.
Round-trip airfare between SBO and LAX is $200.
There are about 3.66 million passengers annually between SBO and LAX per wikipedia. Assuming they're all round-trip passengers, that comes to $732 million in annual revenue generated by this route.
Assuming no inflation, and assuming all that air traffic would opt to take the high-speed rail line at the same price point (a truly heroic assumption), it would take about 100 years to break even on this boondoggle. This excludes the costs/unemployment etc. associated with zero airline traffic.
Assuming no inflation, ... That's what liberal dems always say, while they know the new estimate of $77 billion is far short of what they know will cost over $100 billion. That $77 billion estimate covers some money already allocated to portions of the rail project, but the money was diverted to non-rail related projects. So that money must be replenished and will drive costs over $100 billion including inflation.
They can't even decide how to get the high-speed rail from Merced to San Francisco. One problem is how to get high-speed trains to share track with existing trains like CalTrain into San Francisco's TransBay Terminal. The train platform is an empty hole in the ground, blocks away from the existing CalTrain station; they diverted money away from building the train platform level into finishing the bus station and park levels. Now they are thinking of building a new tunnel from the TransBay Terminal to connect to rail several miles away because of the track sharing problem - the sharing problem will slow the high-speed trains to a crawl up the peninsula to downtown SF. These "high-speed" trains will never get passengers quickly from SF to anywhere.