I also read that FR are to ground 2 aircraft and crew in TLL for a day in November. Very unlike them to do it.
Based on selling tickets for €100 each way plus everything that will be sold on flight over and back then you are looking at a return flight generating €40k plus per aircraft. They also stated that it may be more than 2 aircraft involved.
As for very unlike them fraid you wrong as they have previously provided extra flights for Cheltenham / Munster and Leinster rugby games without a problem where there was no way of picking up return booking once there. Having crew stay over is sensible decision.