What's a luxury home? Not trying to be an ass. When people start throwing around meaningless terms without qualification, normally they are trying to invoke a reaction and aren't too concerned about reality.
If 50,000 new 1M homes are built on the greenbelt, are those luxury homes? Does Nobbie sell his smaller home worth more in Toronto to move out and free up some money? Was the expensive Toronto home a luxury home or just a normal home worth a hell of a lot of money?
I think the answer substantially lies with axing of R1 zoning. Make every sfh home lot eligible for three or four dwelling units by right. Ignore any NIMBY neighbours. If Toronto wants to make money for "affordable" housing, substantially hammer any building permit for a dwelling over 1000 sq ft as that is mostly luxury, status and investment. Those that want it can pay. You want a 5000 sq ft max building envelope in Forest hill to replace the 1400 sq ft existing, no problem, DC of 1M. That 1M roughly pays for construction of a three-storey, four dwelling walkup (if you can get the land from somewhere). I still think some form of partnership is viable. Nobbie signs up, money from program replaces his house with four-unit walkup. He gets ground floor to live in (easy accessibility for aging population), one to rent out (retirement income), program rents out other two units to generate money for next project. When he wants to sell, he has two-units to sell that are worth roughly what his original house would have sold for. It cost him nothing, he got income and a house that is conducive to aging, three more families are housed, no green space destroyed.