Comment by seanmcdirmid

> The megacities you mention are enormously economically productive per capita. All sorts of efficiencies pop up when a huge number of people live near one another.

It isn't a bad thing. NYC and Hong Kong are nice cities, they should exist. But don't expect housing prices to fall because you add more density if demand isn't fixed, the opposite often happens instead (people want to live in megacities even though housing costs are high). And that isn't really a bad thing, like gentrifying a blighted neighborhood will drive up housing prices as well.