IMHO the key problems is new building is not targeted to the affordable market and easier to build areas with access to jobs of good economic income are not really open any longer. The established land markets are more expensive because literal "green field" expansion of new cities is not very common, and no longer available in quantity. The cost to build are further increased because the higher end market demands more amenities and developers almost always target the highest market available.

Note: I have a personal theory that one way China was able to perform at this it's current stage of growth, was because it was expanding a lot of first generation real estate development to new areas. It will be very interesting to see if they are able to maintain low housing costs going forward into the next couple decades.

There are dubious claims that the lower end market will be served by aged-out high end market housing and that's simply not the case. It ignores that housing stock ages out of usability - and remodeling is often more expensive to work on than the initial builds. Once you remodel them, they occupied at the high end, then they never free up or go down in rent for other portions of the market.