Unit cost factors must be updated frequently to remain current with changing costs, areas, and inflation. Some sample unit cost factors (and values) are: Total average cost of operating an automobile (52 cents per mile), Cost to bury fiber cable in a suburban area ($30,000 per mile), Cost to construct a parking space in a parking garage ($4,500 per space), Cost of constructing an interstate highway ($6.2 million per mile), Cost of house construction per livable area ($225 per square foot). If house construction costs average $225 per square foot, a preliminary cost estimate for an 1800-square-foot house is $405,000.