Good question

My 5 yr old: What if everything were free?
Me: They kind of tried that already, it was called Communism. It didn't work out too well.
My 5 yr old: No you made that up!
Me: No, no I didn't.
My 5 yr old: Yes you did
Me: You'll learn about it in school someday...

.....My unsaid thoughts, "unfortunately his teachers will probably tell him what a great failed experiment it was..."