NASA awarded flights 7, 8, and 9 for Crew Dragon in an extension of the existing contract, bringing the total value to \$3,490,872,904 . We know that in 2014 SpaceX was awarded about $2.6 billion to develop and fly Crew Dragon, at least the first two Demo and first operational flight were included in there.
Bottom line, how much did these 3 additional flights actually cost?