I've used the airport ATM often. My Credit Union issued card does not get charged a fee. And I have never seen a fee on my receipt from NCB.
However, the Scotia Bank charges me a fee. A couple bucks US$. I will continue to use my ATM card and hope all the banks don't follow Scotia Bank's lead with fees. I love the convenience.

There are ATM's scattered around Negril that are not associated with a bank. Cool Money, or something like that. I've seen fees of $6.00 on them. So if you have your own bank's fee on top of that --- that definitely gets expensive.