[MalcolmTucker]

No matter what system is built, a huge initial fixed cost is the operation and maintenance centre, which includes storage tracks, light maintenance bays, and overhaul bays. Unfortunately they don't scale down very well, I would doubt including land costs even for a small system you could get costs down to less than $100 million.

Tracks can really range in price. In Toronto where they had to do very little utility relocation, with no signal system, no powered switches they built 7.5 km of dual track for ~$100 million, not including rolling stock. For street running utility relocation is usually the highest cost which makes it hard to predict costs without an underground services map.