The way I understand it and play it is to pay for each model you have once.
So a carrier with two flights of aircraft is carrier cost + plane cost + plane cost = total. Its no different than having three destroyers are paying a cost for each one.
What confuses me is this reference on page 11 of the advanced rules under Fleet Construction Etiquette: “Carriers and their Aircraft squadrons can attack enemy units anywhere on the battle map, but you’ll have to pay for them twice: once for the Carrier, and once for each squadron you assign to it.” :?
It is a case of poor wording. I suspect what they were trying to say is that to use planes, you have to pay for both the planes and the carrier, you do not get the planes with the carrier. If you still need help, post the question over on the Avalon Hill boards under naval miniatures.
Both of these answers coincide with my understanding.
