They've said one pound (sterling) or one Euro, whichever you have on you. So I guess it'll also be one dollar if they come over this way.
Once someone (a man, presumably), has peed on the carpet in front of his seat, and probably down the front of the seat as well, I wonder what it will cost to clean said carpet, or even perhaps to replace it. And whether the acid in pee could cause airframe corrosion. Not to say the cost of down time while this is going on.
I really do expect this will finish Ryanair. Deservedly so - they're little better than crooks anyway.