LO, NaB,
Ok, I didn't even make the cut for Staff College so I'm more than happy to be told why I'm barking up totally the wrong tree on this.
So take the cost of hardware changes to the ship as ballpark 700 million.
Now, pay for the UK to be different, and put a buddy refuel store on F-35C. Pray that the existing pipework in the wing is adequate for the existing F-18 system and you don't have a major re-design and re-qualification of the wing or have to start from scratch with the pod. The easiest possible solution would cost you a hundred million or more (as a rough guess, going by Eurofighter prices).
How many pilots will your frontline strength be? 60-odd? So 15-20/year going through the OCU? Pack them off to the US for a few hours famil in a T-45, then FCLP them, then send them to the ship. I dunno, maybe 6 weeks in the US, so maybe 150k/person worth of training? Call it 2 million a year total. Over the 40 year life of the ship, that's not far off another 100 million.
Buy 2 fully orange-wired early-LRIP -C models to replace the 2 -Bs we've bought. Couple hundred million right there.
Do some frantic contract re-negotiation to get PWIV and Asraam into the -C test Program (paying to be different). I doubt that comes for free. Couple of million in there I expect.
Fuel costs through life - pilots will always empty the tank, so straight away your fuel bill for F-35C is 150% bigger than the -B. Lots of millions in there.
Pour some concrete at the MOB to make an FCLP deck area. Few more million.
Build, staff and run an LSO school and training pipeline for the dozen or so guys to man the platform (or send another 4-6 guys/year across to the US for that piece to?). Another few million.
Recruit, accommodate, train, pay and pension the extra 10-20? (probably conservative) deck handlers, catapult operators & maintainers. Average salary 40k? Another million or more.
That's off the top of my head and I'm definitely not a procurement and DLOD guru. Factor in the fact that everything in defence procurement costs more and takes longer than your first estimate, and I can easily see why the 'cost of switching to cats & traps' is headlining well above 1 billion. And I don't think it's down to a con job by the old enemy of BAE, or some incredibly clever Machiavellian plot by the RAF to make the RN look bad. Could be wrong though.
Regards,
Single Seat, Single Engine, The Only Way To Fly