To put this into perspective, China's high-speed rail project in Indonesia connecting Jakarta and Bandung (a distance of 143 km) at a speed of 350 km/h was completed in just four months at total cost of $7.3 billion.
This line has seen an impressive number of passengers, with approximately 2 million people utilizing the service.
By the time cost overruns, last minute changes, etc etc are figured, id not be surprised if the $100bn quote balloons to 150 or more.