I'm not an urban planner expert, but the logic makes sense to me. I look up my downtown condo vs a suburb home of comparable value, and I pay twice as much in property taxes. It's not hard to understand how density is inherently more efficient.
But, I was talking about the city, society, or the greater good. Whatever you call it. Higher density is more efficient and uses less resources per capita. Period. Same reason private planes are so bad for the environment.
But do you really pay for suburbs? As I said, the cost intensive positions scale with the number of people. Schools, utilities, ...