Is this what this is about?
Yes and no. Yes, in exact monetary terms, no in the sense that this was the last aggravation at the end of a totally tedious and frustrating morning in terms of the hassles getting to the airport, getting through the airport (Dublin) and it's disastrous "security" system, fighting to get through the crowds to get to the gate, trying and failing to get a coffee before boarding, having to get through the rugby scrum at the gate, etc etc.
Ok, in monetary terms, not really an issue, though someone else mentioned £3, which I would be unhappy about, but in attiude terms, if a good few on each flight are treated the same way, it's a "nice little earner" for the cabin crew! Would you accept being short changed in a shop, or on a bus? Probably not, so why is it acceptable on an aircraft?