Following on from the previous post I noticed another link regarding the USMC purchase of B's and C's. The story isn't new but is significant in that it indicates further unit cost increases for the B model.
Five Marine Corps F-35Cs Units to Fly Off Navy Carriers | Defense Update
''Under the agreement, the two services will maintain the planned acquisition of 680 F-35s but change the proportion between the carrier based and STOVL variants. Under the new plan the Navy will buy 260 of the F-35C carrier variant, with the Marine Corps adding additional 80, along with 340 F-35Bs STOVL versions. Reduction of 80 ‘B’ aircraft is expected to further increase the unit cost of the STOVL version, already blamed to be the most complex, expensive and troubled part of the JSF program.''