A good list summarizing the ways in which density is good for affordability, ending with this zinger:
Income inequality is the core reason why housing affordability is such an intractable problem in the United States. In pretty much every other industrialized nation on earth, greater redistribution of wealth helps ease the problem of affordable housing. This includes social investments that significantly reduce other major household expenses, such as healthcare, education, childcare, and transportation, thereby freeing up more income to pay for housing. Here in the U.S, we will be beating our heads against the wall forever trying to provide enough affordable housing to make up for this underlying inequity.
Painful because it’s true.