Here is a good article, look at the last myth
http://www.yesterland.com/monoraillegends.html
It states the Las Vegas Monorail in 2004 cost $654 million for 4.4 Miles. This would be more true to life than comparing it to Disney Monorail, since like Las Vegas Uni would have to deal with property owners and right of ways like Las Vegas did.
Which Ironically doing quick directions from point A to point B it shows around 4 miles....so with everything it would also be around 4.4 miles