eDIT Looks like you are right for the US. In other countries it's apparently much cheaper.

https://www.hsrail.org/blog/why-transit-projects-cost-more-i...

> For example, the Purple Line in Los Angeles cost $800 million per mile. By international standards, the New York price tag is stratospheric: A project in Madrid cost $320 million per mile, and one in Paris cost just $160 million per mile.