“Costing around €3m (£2.4m) and funded mostly by the local authority, the road is made up of rows of crystalline silicon solar cells. … When the path is extended to 100 metres in 2016, its creators hope that it will produce enough energy to power three households.” (http://www.theguardian.com/environment/2014/nov/05/worlds-first-solar-cycle-lane-opening-in-the-netherlands)

€3m for three households seems steep, especially in The Netherlands.