ALPA's only "part of the bargain" is to be the legally recognized bargaining agent for a property. That said, they have no legal obligation other than to assist the pilot group with bargaining. Everything else is extra. Since dues are collected only on wages earned, and that money is gone...
Besides, if they refunded money, how could Prater afford to take his family and a bunch of cronies to the IFALPA conference in New Zealand? Or the fancy cigars and dinners that he an Helling enjoy so much? After all, he's a "big time union boss," right?