I think you are close. To my knowledge, there can be no charge for an audience for a TV show. Some Fed stuff. It is possible that FOX found out about the charge too late to check to see if the minimal charge for a different party would be OK or not. FOX understandidly (sp?) pulled Hannity rather than risk millions dollars of fines.
Why does everybody get so upset with FOX, Hannity or whoever before the facts are known? It happens so often!
Because they are in the business. They know the rules. Someone should have checked in the WEEKS they promoted the thing.