First, I just noticed this a World Jamboree, not just National. Now I wonder about language skills, etc.
This is a struggling nonprofit, not a corporation with shareholders and dividends. Any waived expense is paid for by someone else. $$ to run the program comes from scouts, parents, adult volunteers, and charitable donations, with a little fundraising added in. (Pancake breakfasts, popcorn sales, etc.). And corporate charitable support has taken a tremendous hit over the last couple of decades.
Waiving collection of funds does NOT eliminate the expenses that the funds cover. And there are plenty of other trained volunteer supporting the operation. I bet a significant portion of the medical staff at the event will be volunteers. Any support position that can be staffed by someone just showing up for two weeks is likely majority volunteer. None of them are more special than the others.
At local camps, a huge amount of maintenance and even upgrades are done by volunteers in the trades donating time, materials, and expertise.
Yes, on smaller scales it is possible to just provide a no charge place to put up a tent, and there may be a budget to cover some meals, but the size and extent of the Bechtel operation is far beyond that. Gone are the days when scouting benefited from the free (and even subsidized) use of Fort AP Hill every 4 years.
FYI - you touched on a sore point for me.