GAO: NASA Faces Challenges Defining Scope and Costs of Space Shuttle Transition and Retirement
"The total cost of SSP transition and retirement is not transparent in NASA's current budget request and is not expected to be reflected in its fiscal year 2010 budget request. This is due in part to delays in estimating costs, but also to where costs are being reflected. For example, although SSP's direct transition and retirement costs are identified in the SSP budget line, indirect costs related to environmental clean-up and restoration, maintenance of required real property facilities during the gap in human spaceflight, and demolition of excess facilities are not. In addition, NASA plans to offset some transition costs by utilizing an "exchange/sale" authority that allows executive agencies to exchange or sell non-excess, non-surplus personal property and apply the proceeds toward acquiring similar replacement property."


And, of course, a lot of the costs for transitioning to the Ares launch vehicles are still being worked out, given that the launchers are, themselves, still very much a work in progress. Overall, I think that no-one is too sure exactly what the cost will be just yet, both in terms of cash and in terms of jobs, for the change-over.