I think the number of times passholders use their APs has no effect on the cost of the pass. At some point when they go into the park, they will want to purchase some sort of refreshment - be it a snack, beverage, meal, perhaps even all of the above. Therefore, the park is making a profit on them in ways other than mere presence (admittance). And because someone like that guy goes so often, assuming he purchases anything, they are actually earning more profit for his determined attendance.