Exactly. It makes no sense. The area is mostly low density industrial, highway-like, and it's ugly as all hell. The Vaughan portion particularly. The section between Sheppard to north of Finch, and from Steeles to Hwy 7 should've been run in the open air (elev, trenched, etc). I'm quite confident no other city would ever consider building the costliest of all transit infrastructure in such an environment...Toronto really stands out in that regard.
Montreal is the only example that I can think of (Laval extension), but they did that because they have to be underground because of the technology they chose. It's also a single tunnel bore instead of twin like Spadina.