Probably not nearly as much as the billions in overruns
on the ISS itself. NASA mismanagement screwed the pooch really bad on the ISS. With no mandate for increased NASA funding from the public at large nor from politicians, something had to give. Given NASA's dismal track record at managing large projects (virtually all of them in NASA's history have been over budget and/or very late), it's hard to see giving them even more money to waste.