Interesting article, particularly the last line.
SpaceX has a $1.6 billion contract with NASA for 12 flights to the ISS.
A shuttle flight costs what about a billion per trip? If SpaceX can deliver that is quite a savings.
Actual space shuttle flights cost about 40 million each.
The "one billion per trip" includes the costs of the massive infrastructure to support it. In short, if you don't fly the shuttle, you don't save one billion dollars per flight because that massive infrastructure (including thousands of people who work on the shuttle) have to be paid whether its flying or not.
Every shuttle flight you don't make saves only about 40 million dollars.