We have had these talks from age 4 onwards when DS started to understand what being rich and poor means. He is severely affected by the thought of homeless children, hungry children, homeless adults and poor people. He once told me that he hates billionaires because they like to amass all that money for themselves and they don't share! Needless to say, we have had many discussions on capitalism, free market economies, socialism, communism etc. I have pointed out the contributions of philathropic billionaires who have taken up causes that governments could not fix.
I always say that being rich and poor are relative. Our family has enough to eat and live on compared to billions of other families (especially in the third world) - to them, we look very rich. I also tell him that I consider our family not rich compared to people with millions and billions of dollars in assets. I tell him that we belong to a salaried class of people who depend on their paycheck and the hours we spend for the employer for the money we make. He comes back and asks how we could afford a house, an xyz brand of car, school fees, extracurriculars and good quality food - I resort to humor and tell him that those are the reasons we are not rich - we spend all our money on those things with nothing more left in the bank