In terms of material costs for the structure, no, high rises aren't the optimum of affordability. But when you factor in the infrastructure requirements on the

In terms of material costs for the structure, no, high rises aren't the optimum of affordability. But when you factor in the infrastructure requirements on the scale of demand for "the city" you can easily find that building miles and miles of brownstones gets you the worst of both worlds - you need to maintain the infrastructure of high rises with public transit, cleaners, etc but you are only getting a fraction the density you could if you spent more on the building. You can think of it from the perspective of how cities grow - there is pressure inward to grow up the core and people will push from the outsides in. That push can result in low density sprawl or upsizing density, but they are pushing in to get closer to the actual city core where maximum interconnectedness and locality can happen. In the naive way most US cities have grown individual townships and developments manage themselves and protect their own to the detriment of the whole. Its how you get situations like what Strong Towns talks about all the time[1] where sprawling out has quadratic expenses. As metro areas grow, and certainly when you are in the tens of millions, you are looking at spending preposterous amounts of money on your suburban infrastructure that way eclipses the per-unit costs of building denser buildings in a smaller footprint. [1] https://www.strongtowns.org/journal/2016/9/18/more-math https://www.strongtowns.org/journal/2016/9/18/more-math