Is that really true? For a simple example, it looks like a simple surface light rail line in the US typically runs about 100M/mi. That's pretty much the same as what it costs in the UK.
There's no reason we pay such high taxes and have so little to show for it. I get tired of the endless excuses. Every other country--even the more expensive ones like Switzerland--have more effective infrastructure projects. I honestly don't even think this is debatable. Go look at how poorly maintained practically everything in the state is--schools, roads, bridges... It doesn't make sense when we're paying such high taxes and have all the big tech companies here... I don't know why people are so comfortable with that cognitive dissonance.
The Chinatown subway was $600M/km, which is 3-4× "reasonable" construction costs, and fairly far from the most expensive subway, which is I believe NYC's Second Ave phase 2, at almost $4000M/km.
The US in general is a high-cost construction country (for a variety of reasons), but relative to the rest of the US, California is neither particularly expensive nor particularly cheap.