Did you factor in the free peanuts?
...and the avalanche of French Fries?
Five Guys is NOTORIOUS for French Fry overload; a large order of fries comes in a 20oz soft drink cup, which they put in a sack, then bury with more.
I was traveling with my son in Kill Devil Hills, NC last year and stopped into the Five guys out there. Each ordered a burger, drink and large fries — our order came out in two sacks and one of them was just for the fries: two 20oz cups full and buried 3/4 of the way to the top.