The solution of course is to build more, but it just happens that the private initiative always build under demand because it is inelastic and it's in their interest to keep the market as so.
Of course the Vienna success came from public intervention because otherwhise you'd have exactly the same situation of hundreds of other cities where rent is always a hefty amount of modal income and no matter how easy and cheap is to build it just happens those with access to capital never meet demand.
You need to build more, in many cite MUCH more, and you need vacant housing so floating population can come and go easily.
Of course the Vienna success came from public intervention because otherwhise you'd have exactly the same situation of hundreds of other cities where rent is always a hefty amount of modal income and no matter how easy and cheap is to build it just happens those with access to capital never meet demand.
You need to build more, in many cite MUCH more, and you need vacant housing so floating population can come and go easily.