I have no first hand knowledge on the costs of putting together SnF or Oshkosh. That said, both are huge events and require a tremendous amout of support and organization. I imagine their expenses include:
Staff Costs
Campground facilities - purchase cost and upkeep.
Porta Potties.
Adverstising.
Printing expenses
Equipment Rental (Trailers, canopies, vehicles, etc.)
Insurance.
General maintenance (cutting the grass, for instance) on the grounds.
Fencing.
Security
Facilities (Display halls, forum spaces, etc.)
Appearance fees for airshow acts and/or speakers.
Shuttles and Buses
Waste Disposal
Emergency Services (e.g. medical tent).
In addition, both the EAA (Osh) and SnF (certain Florida EAA Chapters IIRC) use their fly-ins as a fundraiser. I can't really object to either organization making a buck off me to further their aviation related pursuits.
Kyle
You forgot about feeding the volunteers! We eat a lot! Sun N' Fun seems like it's being over run by the corporate sponsors the past 4 years. Several years ago, there was nearly a volunteer revolt. This was due to the corporate sponsors desires for space at the expense of the volunteers.
Don't they also provide fuel for some of the cool vintage military aircraft which are displayed?
Alas, last minute business prevented me from attending this year! :-(
Charlie Kuss