It has generally been assumed that NASA will save money by spurring the development of services by US companies to supply the International Space Station, but such conclusions have largely been based on estimates. Now, a rigorous new review authored by a NASA analyst, and published by the American Institute of Aeronautics and Astronautics, offers a clear answer to this question.
According to the new research paper by Edgar Zapata, who works at Kennedy Space Center, the supply services offered by SpaceX and Orbital ATK have cost NASA two to three times less than if the space agency had continued to fly the space shuttle. For his analysis, Zapata attempted to make an "apples to apples" comparison between the commercial vehicles, through June 2017, and the space shuttle.
Specifically, the analysis of development and operational expenses, as well as vehicle failures, found that SpaceX had cost NASA about $89,000 per kg of cargo delivered to the space station. By the same methodology, he found Orbital ATK had cost $135,000 per kg. Had the shuttle continued to fly, and deliver cargo via its Multi-Purpose Logistics Module, it would have cost $272,000 per kg.