I heard on TV (or read somewhere) that it cost $60 million to shoot down the satellite. (See this article from Slate, "The $60 Million Missile: Why is it so expensive to shoot down a spy satellite?".) Also, check this out from The Left Coaster (quoting from the science journal Nature):
A plan by the US government to shoot down an out-of-control spy satellite has been described as a cynical tit-for-tat move in response to China doing the same last year. Scientists and arms-control experts fear that the operation will create damaging debris and weaken international efforts to ban space weaponry. . . .
But scientists familiar with both satellite re-entry and the US missile defence system question the decision. The chances that the tank, which is 1 metre in diameter, will survive and strike land are extremely small, says Geoffrey Forden, a physicist at the Massachusetts Institute of Technology in Cambridge. “Most likely it will land in the ocean,” he says. The reasons given for the plan “don’t sound too credible to me”, he adds. “I think they’re doing it mainly to tell the Chinese that we can blow up a satellite too,” says Jonathan McDowell, an astronomer at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts. “This gives the US cover to carry out a test.”
So Bush's defense contractor friends got a boost (remember the $6,000 toilet or however much it cost?) and Bush got to thumb his nose at the Chinese. (According to Slate, $60 million is about 0.01 percent of the 2009 budget for the Department of Defense.)