Getting serious for a moment, there are usually fees involved in any public gathering. Some of the fees I've come across when being involved in the car show promotion scene are:
Rental of the facility,
security,
guaranties to venders,
portable toilets,
clean up and trash pick up costs at the end of the event,
in some cases it's necessary to get the city or country to run temporary power,
in today's world many facilities owners are requiring that the shows promoters purchase event insurance that covers liability, property, and in some cases, even workers comp, if the property owner of municipality has to supply manpower for the event.
Then there's the cost of promoting the event, posters, fliers, radio and/or spot announcements,
awards,
refreshments for the staff (even if they volunteer their time), most times there are "staff" tee shirts
Event tees
Dash plaques,
Trophies,
and a bunch of other stuff. In some cases even the local police charge for the additional man power needed to cover the event.
I'm not intimating that all event's have all these costs, but hardly any event is free of costs.
Whether or not the entry fees are justified is another matter.
Someone mentioned that the promoters should pay us to bring our cars to the show. If that were to become the standard, I doubt that there would be any car shows.