Yes, there are many factors. What I couldn't understand (and what I think my "brainwave" explains) is why excess demand barely moves the needle of supply. Usual

Yes, there are many factors. What I couldn't understand (and what I think my "brainwave" explains) is why excess demand barely moves the needle of supply. Usually if something is in short supply, it becomes more and more economical to produce it and sell it - increasing supply and decreasing prices. Some of the factors you list decrease supply, but to me, the elephant in the room is that we don't seem to be able to create new cities - thus we're all competing for a fixed, small supply of land near the centres of a handful of high-status cities. Different zoning, REITs and public transport are factors too, but these are merely resistors in the circuit, not switches IMHO.