Our pack, for normal campouts, solicits a token amount to help with the costs of food. I don't know what the per person cost is, but they cap each family at $25. Since my family is 4, we also only have to pay the $25. Now, we are going to the Yorktown in December, and because of the high cost of the trip, each family had to pay the $60/person.
Nobody minds, because all other costs (registration, advancements, Boys Life, etc) are paid for by the pack.