Others have said that the $350,000 is reasonable - but let me point out that there can be a wide range of "2-line roads", even in a small area (so same cost of labor, gravel, concrete or asphalt, etc.).

Some rural "2-lane roads" are two barely-wide-enough lanes for vehicles, with no shoulders, no curbs, and drainage ditches (so no buried storm sewers or anything). Curves can be sharp, grades steep, and blind summits frequent. Bridges may be 1 lane wide, or have weight limits.

Vs. "2-lane road" in even a modest little city often implies pavement wide enough to park on one or both sides of the 2 traffic lanes, and a load of other expensive upgrades. I'd not be a bit surprised if the cost per mile of that was 2x to 5x the cost of a bare-minimum rural 2-lane (paved) road.