Total Project Costs: For commercial installations, expect costs ranging from $5,000 to $20,000 per mile for underground projects and from $40,000 to $60,000 per mile for aerial installations. The main cost drivers are materials, installation time, and environmental factors that affect trenching, conduit, and terminations. This. Fiber optic construction is bringing high-speed internet connectivity to homes and businesses in cities around the world. These networks are constructed both underground and through aerial fiber, at an average cost of $1,000 to $1,250 per residential household passed or $60,000 to $80,000 per mile.