Toronto's problem (and to an extent the other major cities in Canada) isn't so much about the salary differences with SV so much as the entire tech ecosystem. The money and cost of living would probably affect decisions for people outside of the GTA trying to move here. But because Toronto is the largest city in the country and is the focal point of Southern Ontario, it could do well by simply retaining the talent it outputs.
The brain drain from the GTA and Southern Ontario has long been real. But alternatively, many people move from other places to Toronto. What makes it difficult for new grads and industry veterans from keeping shop in Toronto is that the mobility and learning experiences aren't there. There are a limited number of high-tech jobs here and anything else is likely in the medical, law, finance, or even media world. In that sense, I wouldn't even classify tech as a second-class citizen so much as being far down on the totem pole.
I partially wonder if the general inferiority complex of Torontonians/Canadians has created this effect. Because the city typically lusts for things from other places (such as SV or NY), it never develops its own reputation and chooses to be itself. Because of that, tech has never developed an identity because all of our tech talent chooses the shiny opportunity granted to them by some company because it's "from Silicon Valley". Just think of what the tech ecosystem would be like if all Torontonians simply stayed here.
For instance, I often posit what would have happened had the ML/DL community had stronger partnerships with AMD as opposed to building everything with CUDA/NVIDIA. AMD, afterall, is just up the street from the University of Toronto in Markham. A symbiotic relationship could've been built with Hinton's lab.