To taxpayers: Less than $50 million, for initial studies.
Total cost is approx. $6 billion, with virtually all of that being financed privately, along with a $1.2 billion concession fee paid by the private company to the state for the operating lease (the state will maintain ownership.) Part of that $1.2 billion will probably be used by the state to upgrade roads connecting the TTC to urban areas, the remaining surplus for non-related road projects.
That's not bad. I'd probably be in favor of that if I lived in that area.