He didn't actually said that, he said he forced Xabi to play in the UCL which will make him cup tied. Xabi initially didn't want to as he wants to move to Arsenal and had a personal agreement, but Benitez convinced him that he needs him for that match against Standard Liege which Liverpool needs to qualify from.
He was then cup tied and then he didn't move to Arsenal, maybe for that reason or maybe Wenger tried to cut the price down since he's cup tied.