That's cute!
My son was the ultimate tightwad. I took him jeans shopping when he was 12 at Dillard's. I pointed out that he could buy one pair of levi's or two pair of Dillard's brands for the same price. The solution was pretty simple for him: "Mom, can I get one pair of Dillard's brand and have the rest in cash"?
He and my father went camping. My dad stopped for gas, and filled up. When he returned to the truck he asked Bradley if he was short on money for the gas, would Bradley help pay? Bradley said..."No Grandpa, I shouldn't have to pay for your mistake". Ah, the wisdom of a 10 year old!