The price tag quoted from NASA is $79M for the entire program...
The program main purpose was to launch the LDO (Lunar Reconnaissance Orbiter). So someone came up with the idea and attached the LCROSS (Lunar Crater Observation and Sensing Satellite) between the LDO an the Centaur booster required to drive the unmanned vehicles into lunar orbit and beyond. I said beyond because the LCROSS as well as the Centaur booster took up a large Earth/Lunar polar orbit after injecting the LDO into a semi-stable moon orbit. This was required to gain the extra velocity for impact (5,600 MPH) as well as to hit the target area identified in the Southern polar region. NASA used the expendable Centaur booster and placed a rather small additional payload (LCROSS) and sensors for the additional $79M including operational expenses, overhead, as well as program overruns.
So really the additional expense to the $500M for the LDO program for it's life, is rather small in standard space exploring budgets. And if you look at a comparison to some of the single AIG bonuses, it's a bargin!