That's because companies only build new housing in booming areas. Plus, it's incredibly rare to get a large amount of housing "at once" in a metropolitan area,

That's because companies only build new housing in booming areas. Plus, it's incredibly rare to get a large amount of housing "at once" in a metropolitan area, such that you could see the effects. IIRC, there are studies that show that places that built more housing had smaller price increases than economically comparable places that built less housing.