I'm no engineer, but I think your estimate for the monorail is a taaaaaad bit off. Check out WVU's PRT costs just to compare...
From wikipedia "...it was not until 1974 that the system had matured technically. Construction of the first guideway in Morgantown started that year, and was completed the next. The "Phase I" system consisted of 5.2 miles (8.4 km) of guideway, 45 vehicles, 3 stations and a maintenance/control facility and cost $62 million.[6] There were large cost overruns during the initial development of the system.[7][8] The system began operations in 1975, with a total expenditure over $60 million, four times the estimate."
60 mil, in 1974.