"Liar" is not a very scholarly word, but I don't know how else to describe some of the comments that come from public officials. It's not just the farm bill, check out this paragraph from a Washington Post story today on the Virginia highway project:
"Project officials hailed the interchange as 'on time and under budget.' But although the mid-2007 target date for completion was met, the final cost was nearly three times what was first projected. A more recent cost estimate of $676 million was ultimately met."
Well, of course, the final estimate was met because it's the final estimate. Obviously, what's important for taxpayers is that politicians and government agencies stick to the numbers that they agree to when they first vote to approve projects.
It is my view that in many, but certainly not all, large government projects there is deliberate subterfuge about ultimate project costs. Many projects balloon in cost 50 percent or more.
For more on cost overruns, see this and this.