Earlier quoted context omitted.
> incentivizing developers to build affordable housing But that's unnecessary. If developers build more luxury housing, that'll reduce the price of existing housing, such that it becomes affordable.
That (first) either assumes demand remains constant, or requires measuring actual cost vs theoretical cost instead of simply actual; and second, assumes that there aren't complex interdependencies - ie, more luxury housing can make an area more desirable and increase demand more than it increases supply - arguably that's the goal , since otherwise you're literally building places people want to live in less than what…
Depends how big the "area" is that you're thinking about. The effect of increasing housing supply is well-studied. Demand can only grow as fast as the population does. If one area experiences increasing demand, then another area will have decreasing demand, comparatively.