Let's not add commercial value, this is about solving real problems, not making money. The constant mixing of those two is what creates problems in the first place. There is no problem in having a an economical positive impact with a solution, but not solving a problem purely because it would "only" solve problems for many people instead of also making a ton of money is a bad way to live (at least, that's what it looks like).
You seem to have misunderstood my point. As density increases it is easier to build subway stations because the value measured in terms of money or units of abstract social benefit goes up proportionally to density.
That does not imply subway stations should not be built in low density areas, it is just an observation that as density increases subway stations are easier to build.
