I was also wondering this. There seems like a pretty good case for the headline, but the more interesting question from the article is whether funding the GSA through some alternative (appropriations) would save the government money compared to the IFF. Which may come down to the kind of behavior the IFF incentivizes, whether it be corruption or self-serving yet legal optimizations. The information you provided about the base rate would have benefited the article by giving some idea of the scale on which the GSA operates.