Used Car Salesman

Nathan has several friends who own Nintendo DS portable game systems.  He wants one, too.  They cost $130 - $170, depending on the model, plus game cartridges.  I'm thinking about birthday, but Nathan's thinking NOW.  I told him we'll have to see what happens for his birthday or Christmas.  He decided to take matters into his own hands.  He's been VERY helpful lately - taking out the trash, cleaning up his room, cleaning the TOILET - all without asking.  Of course, when we commented how helpful he's been, he told us he's working for a big allowance - so he can buy his "DS".  I told him his allowance was a privilege and that his participation in household chores was part of his responsibility as a member of our family.  I would be giving him his usual allowance ($3), and any extra work/pay would have to be negotiated beforehand.  So, after his shower (yes, he prefers to take showers now) one recent evening, he lined up all of his AND EVAN'S remote-controlled cars and trucks along with some non-electric vehicles and began hawking them to the family.  "CARS FOR SALE!!"  "TWO FOR TWO DOLLARS!!"  "GET YOUR CARS FROM NATHAN'S CAR DEALERSHIP!!"  As I went to check on him, Evan was giving him two dollars - to BUY BACK HIS OWN CARS!  When asked what he was doing, Nathan informed me he was selling used cars for DS money. (Reminds me of my brother selling mardi gras beads to the neighbors for a dollar each.)