First was the 2009 Jacob's risk analysis report commissioned by the FTA. It said this:
At the present stage of pre-Preliminary Engineering, one can be 90% confident that the proposed project will cost between 5.2 and 10.2 billion dollars (Figure 1-1, page 1-10 of Jacobs report.) Once PE is done and the project enters Final Design, then its price tag is expected to narrow: The project will have a 90% chance of being built for a budget ranging between 4.8 and 8.1 billion dollars.
Read more here: http://fixoahu.blogspot.com/2009/07/jacobs-report-for-honolulus-proposed.html
In December 2010 Gov. Linda Lingle released state-funded study on the costs of rail. The Star Advertiser summarized it as follows:
The proposed 20-mile rail transit system is likely to cost the city an additional $1.7 billion over the next 20 years, raising the total price tag to at least $7 billion, according to a state review of the project's finances. And there is "substantial risk" that the $1.7 billion additional cost could grow to $4.5 billion.
Read more here: http://www.staradvertiser.com/news/20101203_Cost_will_balloon_rail_report_finds.html
My take quoted in the Star Advertiser is this:
Prevedouros said the analysis was consistent with the 2009 Federal Transit Authority report prepared by the Dallas consulting firm Jacobs Engineering Group, which placed the estimated cost of Oahu's 20-mile system at $5.29 billion but also indicated that there was a chance that the cost could reach or exceed $8.1 billion.
"(Jacobs) did not have a stake in the game. They were just reporting a number," Prevedouros said. "They're experts in getting it right, and they said there was a high chance of overruns. I would trust them more than I would trust advocates of the project."
Prevedouros said the results of the latest analysis should give lawmakers pause as they consider whether and how rail should proceed. "It's a different Congress. This will give them pause. It's a perilous path heading forward."
Read more here: http://www.staradvertiser.com/news/20101203_Train_opponents_cheer_prediction_of_cost_overruns.html
It is important to mention the impeccable reputation and expert subject knowledge of the primary authors of the report prepared by Infrastructure Management Group, Inc. Steve Steckler is Harvard University planner and chairman of IMG with past service in the U.S. DOT. Thomas Rubin is a mass transit consultant who's served as Controller-Treasurer of the Southern California Rapid Transit District, now known as Los Angeles Metropolitan Transit Authority.