Averages out about 250 lbs per person is my measurement. This does not include water which can easily double the load. Then you have fuel and vehicles...
Just two of us with two vehicles and full tanks was around 4000 lbs payload in my case. I easily had an additional 1500 lbs of people, tools and parts in the truck that I did not carry in the trailer. GCW was around 20K lbs with a 7250 lb truck and 7500 lb toy hauler when loaded.