These resorts fees are a racket, that if memory serves started with the Manhattan Club and then spread to many other RCI resorts.
Who pays them varies. I remember one time exchanging into a resort on the French Riviera in summer through DAE Europe. The people in front of us were RCI exchangers and they were charged a significant resort fee but we were not. It turned out that this resort treated DAE exchangers like owners or their guests, who were not charged that resort fee. So with that resort, which exchange company you used also mattered.