The key word was “relatively.”
“The cost estimates in the NDAA for the cheapest version of the F-35, the Air Force’s F-35A, are the following. (Note these costs as just for production and do not include R&D.). “The 2014 procurement cost for 19 F-35As will be $2.989 billion.”
Well relative to that I would say it is a whole lot cheaper. 8>)