That cost is so extreme I feel like I'm missing something, or there's more to the cost. The entire annual budget of California is $350 billion, so even if this is spread out over the next 10 years we're talking about ~7% of the annual budget going to a single transportation project.
This will run LA to SF. If you take the populations of both of those cities (who will benefit most from it) it's 18 million people. So we're talking about costing 231 billion / 18 million = $13,000 per person to build the thing. How is that worth it?
I just looked up and I can get a flight from LAX to SFO for $70. For $13k I could fly back and forth between them almost 100 times.
If that's a real number, as a CA taxpayer (which I'm not) I would be asking where else that money could go. Like increasing the state's education budget by 20% for the next 10 years. Or helping both cities handle their homeless problem.