That's not how supply and demand work. The builders make new, usually expensive housing, the people making enough to afford them move out of their older cheaper

That's not how supply and demand work. The builders make new, usually expensive housing, the people making enough to afford them move out of their older cheaper houses into the new ones, those older houses are now on the market, people who can afford those move in, freeing up cheaper ones, repeat, bottom of the market has new openings.