If they understand money, ask them what they'd buy if they had as much money as they want. You can buy up everything on a shelf, everything in an aisle, everything in the store. But then what will everyone else buy? How hard will people fight for what's left? How much money would they be willing to spend?
Easy money leads you to irresponsibly buy more than you need at the expense of others. If you only had a limited amount of money that you earned through hard work in the past, you become very prudent with how you spend and you have more respect for the things you buy.