F-35C isn't any cheaper than F-35B.
Well seeing as we're already starting to go round this buoy again . . . Dave C may not be any cheaper all-in but it is supposed to be far more capable.
I'll believe the hype about Low Observability + Austere conditions when USAF groundies stop wearing cotton gloves and overshoes when crawling over RAM coated aircraft (which live in conditions that are anything but austere).