Roads alone cost $2-3M/mile and last 30 years. Amortized, that's on the order of $100k/yr/mile.

In a city, that would be $100k / 10 city blocks, probably 100 parcels with 100-1000 low-to-mid rise housing units. In a rural area it might be just 10 housing units, at the cost of $10k/yr/parcel. And productivity in rural areas is 2-3x lower, so it's even higher as a percentage of per-capita GDP.

Add on top of that electric grids, water supply, sewage, emergency services, hospitals, etc. Bottom line: rural areas only survive due to subsidies from productive and overtaxed urban Americans.