It really depends on the agency building the roundabout and the property values at the intersection. For example a rural intersect near me just got a single lan

It really depends on the agency building the roundabout and the property values at the intersection. For example a rural intersect near me just got a single lane roundabout and it cost $3.2 million. The agency building it prefer a lot of concrete over asphalt. Other states can build them for less if they use asphalt.