Modern homebuilders don't build: they use their scale to get land at knock-down rates, slow-walk the planning process, and then farm out the work to actual construction firms at rates that barely keep the lights on:
https://www.thebignewsletter.com/p/its-the-land-stupid-how-the-homebuilder
Monopolists can increase profits by *constraining* supply. 60% of US markets are "highly concentrated" and the companies that dominate these markets are starving homebuilding in them to the tune of $106b/year:
https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3303984
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