To get to 18M number, author approximated that cost of repair 3.5 lane medium use road in industrial area (aka heavy trucks) to all roads in the town which just not make sense. Cost of repair low use residential 2 lane road which is majority of roads in the city is much lower and frankly nobody repaves local roads every 30 years - it just not needed.

In addition $100 per month per house is significant but if it's the only thing that make small town more expensive than dense city it's still does not make city that much attractive.