Of course it is cheaper, that is why every country in the world doesn't bother with these pointless land airfields and just has carriers instead. Oh wait.....
You can bend numbers in lots of ways and use very specific examples, and if you want to have a fast response and happen to fight a country where all the targets are close to (an uncontested) sea but land bases are much further away then a carrier will be quicker responding. Maybe not more capable as you are limited to carrier capable aircraft, or longer on task (but possibly will be). But claiming that, generally speaking, flying aircraft off carriers is cheaper than flying them from land bases is ridiculous.
Anyone throw some figures around for how long a Harrier would take to get on task over Nad Ali from a carrier "somewhere in the Indian Ocean"? 700 miles @M.7 gives 100 minutes (plus the AAR time). Plus how much to support a carrier group in the Indian Ocean? Lies, damn lies and statistics.........
[A deliberate, parochial and biased view to show how you can make sense to a layman but actually have a bollox argument, for those that haven't noticed.]
Don't get me wrong I am a big carrier fan - I think the UK should have 2 full size carriers flying F35C (force mixed with rotary and FW AEW as required), but using flawed arguments to fight the case will only harm it, not help. I also fully agree with the 1SL that all this RN dripping is just becoming corrosive. We/they need to move on and put up a jt fight to ensure that we get the right capability in the future.