I remember seeing one of those post doomsday B movies in the late 1970's. The only thing worth value in a post doomsday world is guns, bullets, cans of beans, and stockpile of quality booze and good quality Playboy/Penthouse magazines that can be sold for a good price to the warlord soldiers roaming the collapsed society.
A Boy and His Dog? From a Harlen Ellison short story?
You still need to have some jack on you in case you run across a 'ville...