It's not that. 

It's that these airframes have required maintenance at "X" hours. They record G's on airframes. So many G's in combat type maneuvers for so long requires extra maintenance. Hard landings require extra maintenance, etc, etc, etc. Extra flying takes airframes out of services. Too many airframes out of service and you compromise your carrier wing. We put tons of hours on airframes in the Red Sea, hard hours, and we expended a significant fraction of our ship-air Munitions. So much so that we switched to Bofors guns for anti drone until we started running out of THAT ammunition. All of this matters, and makes it harder to actually respond to an incursion by, say, China. All the extra hours being put on the Eisenhower and it's air wing and it's Escorts mean that at sometime in the future they are all going to be out of service for repairs and maintenance sooner than they otherwise would have been. It's not about cost, it's about readiness.