Reading the Airport Fees document on the website today, came across this, is this new, or has the passenger service charge always been charged by the airport?
As 10 DME ARC says, the amount the airlines pay doesn't necessarily have any relation to the published price.
As far as I've noticed, historically at least, my tickets to/ from NCL have included a PSC for arriving pax, but not departing. This has been the opposite of most UK airports.
An useful benefit of this has been when booking reward flights on KLM, and paying the taxes, choosing to depart from MME and return to NCL works out a lot cheaper than t'other way around.