They're off by about an order of magnitude. The ENTIRE budget of NASA is somewhere in the $15 Billion range, shuttle missions are not a third of the annual budget a pop.
What else do they have going on their? It is about the only thing that NASA has project wise right now. But you're right. That would be 0.5 Billion per flight not 5. Sorry bout that. I am not relying on my memory any more!!
Still, that's a whole lot more than the 10.5 million they predicted it would cost to launch. Also, if you take into account the $14 billion dollar overrun for the project development, the space shuttle is one very expensive reusable (hah) vehicle.