Michael Grant said this quote

Albert had created a currency based on gold bullets and McDonald’s game pieces. He’d wanted to call the currency something else, but no one remembered what. So, ’Bertos they were, a play on “Albert,” coined by Howard, of course, who had also come up with “the FAYZ” to describe their weird little world.Sam had thought Albert was nuts with his obsession with creating money. But the evidence was in: Albert’s system was producing just enough food for kids to survive. And a lot more kids were working. Far fewer were just hanging out. It was no longer impossible to get kids to go into the fields and do the backbreaking work of picking crops. They worked for ’Bertos and spent ’Bertos, and for now at least starvation was just a bad memory.