Depends on the Championship. The costs can vary greatly.
What is hard to measure for any USGA Championship is the logistics. Transportation, food, putting together a volunteer base to handle a 1000+ details, caddies, caddies, storage, spectator flow, advertising, special events,practice facilities and schedules,programs, media, parking, hotels, communications----the list is seemingly endless and is not only measured in dollars but tens of thousands of man hours . It's akin to putting together a military campaign. I've been involved in many USGA Championships and there is always one constant present in a successful Championship and that is people, dedicated to the point of obsession. Putting the right people in the correct areas of responsibility is paramount. The various Committee Chairs must have unique leadership qualities and the local Chairman of the Championship proper MUST be the correct choice to oversee all the volunteers. Success will start with this person. Money and good people who love the game and are proud of a USGA Championship coming to their area are the prerequisates .