Why don't we use the money and pennies that we get from scavenging to start a real economy? I mean, at the beginning it will be only find by scavengers, but later on, it could be implemented so if someone needs a hammer for example, it cost 1 dollar and 50 pennies... The economy itself could be reestablish by the players!
It needs though the cooperation of all the players as it could enhance the role play experience to!