SciAm online has a short article by George Musser on cost overruns in NASA science projects and their various causes. All pretty standard stuff. It does end with the following sad-but-true aside:
Some finances, though, are beyond NASA’s control. Five years ago President George W. Bush ordered NASA to replace the shuttle but failed to pay the transition costs, forcing NASA to make internal cuts, such as eliminating technology development and delaying projects that were ready to go, which ultimately raised costs. If those who foot the bill expect NASA to make the best use of their money, then it would help if they, too, set expectations in line with resources.