High I'm wondering how much it would be to do high dusting in a church with the ceilings being about 40 to 50 feet high

Impossible to tell. How much area? Who will pay for the scaffolding or lift? You won't do it from a ladder. Do you have insurance, bonding and training for working at 50 ft. 5 stories+? Do you have fall protection harnesses? OSHA regulations are very particular due to fall injuries and deaths. Something like this is best left to professionals who are experienced working at heights