It’s much more complicated than that. If you’re interested, Alon Levy of Pedestrian Observations compares transit construction costs across countries, for example why some countries like Spain and South Korea can build subways for 1/10 the cost per mile of USA construction projects. It basically comes down to “no one tried to make this cheaper”. Culture and history seem to be the primary drivers, more than labor costs, unions, corruption, environmental regulations, NIMBYs, etc.