I don’t know about Australia but the real problem in the US is that the aforementioned interests (homeowners, speculators) have acted effectively like a cartel

I don’t know about Australia but the real problem in the US is that the aforementioned interests (homeowners, speculators) have acted effectively like a cartel to restrict supply. They do this by pulling out every possible objection to block construction permits. Price signals work if supply can raise to meet demand. When house prices go up it becomes more profitable to build, etc. But when the supply side mechanism is blocked for a necessity then prices will just go up, and up, and up… especially if it can also be bought on leverage.