It's advantageous to build dwellings when the market price of dwellings exceeds the costs of land and construction; as far as I can tell this is always or nearly always the case in UK, some planning restriction related abnormalities excepted.
This doesn't fix affordability or even satisfy overall demand.
Demand is also skewed by a whole load of things including investment (i.e. demand) from parties outside of the local economy in which the supply is realised.
It's advantageous to build dwellings when the market price of dwellings exceeds the costs of land and construction; as far as I can tell this is always or nearly always the case in UK, some planning restriction related abnormalities excepted.
This doesn't fix affordability or even satisfy overall demand.
Demand is also skewed by a whole load of things including investment (i.e. demand) from parties outside of the local economy in which the supply is realised.
tl/dr: supply and demand is mainly a myth imo.
Edit: @NickCJ said it already.