There is no "more expensive market" or "secret Ultra-Toronto" that can move downstream into Toronto. Is it just "there are a lot of rich Canadian investors" (seems unlikely) or is it mostly just people overseas buying and leaving places empty and/or hoping to maybe rent it out?
Something doesn't seem to make much sense. What Canadian investor is going to think, hmmm, I'll bid $400k over on a 2.5MM home that no one in my country can afford in the most expensive city and it's not even that nice. Who is going to buy it from them as it goes up? Anyone in Canada who could possibly afford it now, or in the future will already have a nice home, unless are just swapping around for a different location. There has to be some 3rd party upstream they know will buy it out from them, or else they will be the sucker who hit the ceiling with a property they can't sell.