The Skytrain system in Vancouver has shown the real cost per km for Automated transit that can handle 24,000 passengers per hour. The 11 km extension, is in service  under  budget at $1.4B,, this is $127M/km.  By comparison the Spadina - York Subway extension in Toronto is 8.6 km long, for $3.18B.  This extension still in construction will, according to TTC, cost $369M/km.  The Scarborough Subway extension 6km, estimated at  $3.16B comes in at $526/km. 
Toronto do the math.