If the incompetent government(s) estimate it at $5,100,000,000 you can count on it being two to three times that figure.
Bet the taxi, bus, and rental car companies are thrilled too. A lot of locals can watch their jobs evaporate.
Sad thing is, some of these kind of things can be built for a somewhat reasonable cost. Portland Streetcar came in at about $15 million per mile (in 2012 dollars, including buying the cars and the storage/maintenance facilities), although I suspect that private firms could have come in at far lower cost than that. $255 million per mile for something that’s essentially the same kind of thing is beyond absurd.
The taxi and bus drivers don't just drive - they act as tour guides in a way. They will steer you to the "best" hotel, beach, surf shop, t-shirt shack, waterfall, whatever. I'm sure the drivers get something in return for their "recommendations". I bet some tourist traps don't advertise any other way. And I'm sure a lot of them will be nowhere near a railway station.