Have not used Waterford but they appear to have got thus idea from the UK. I have seen this reported a couple of times, the only one I can recall is Norwich.
It sounds as if it's on the same lines as my local hospital that charges visitors £3 for parking and say that it is for 3 hours. Problem being that visiting hours are actually a maximum of 2 hours and you cannot by less than £3.
I would say that Waterford should ensure that their charges are flagged up by the airline as having to be paid on departure. A letter to the CEO certainly has to be in order, not necessarily about the charge but the fact that it is hidden.