Rural areas are actually cheaper because they do NOT have paved roads every 500 feet or so. The local county pays for all of the rural roads (maintenance, plowing, etc) and the little town pays for the roads in town; federal funds are only used for the interstate and some connecting ramps, etc.
What may not be sustainable is city-like road patterns with suburban densities.
What may not be sustainable is city-like road patterns with suburban densities.