Interestingly enough, a Virginia medical examiner has ruled his death to be a homicide (cnn.com) due to wounds sustained in the 1981 assassination attempt, so, theoretically, I suppose, John Hinckley could be looking at a fresh murder charge.
Here's the Congressional Budget Office's latest projections and analysis: http://www.cbo.gov/showdoc.cfm?index=5530&sequence=0 From there, you can click on the links to the different chapters. Here's a brief summary (of the issue, not the CBO study)...