Actually, it's a hell of a lot easier than trying to coordinate 15-20 people to bring something for multiple meals, which would create chaos (too many cooks at once), and also leave us with too much leftover food, like a giant potluck.
With the "teams", it's much cheaper too. A really nice meal to feed 20 can be done for around $50-$60, divided by 4 campers, equals $12.50-$15 spent for FIVE full meals. Really not a bad deal at all.
