The estimated cost for an 11-mile extension of a trolley line in San Diego has jumped by nearly half a billion dollars -- from $1.24 billion two years ago to $1.7 billion now. The increase can be attributed to the addition of a new station, rail bridge, parking and trolley cars that were not part of the original plan. Construction is scheduled to begin in 2015 and finish in 2018, depending on the approval of the project's final environmental report.