I would change some of the items, and the prices are a bit off.
1 new video game = $60
1 month of cable TV = $50
mp3 players aren't positive or negative, everybody listens to music on the car radio
I would also leave books out in order to make a stronger argument.
If I were writing a letter to parents I would explain all about how amazing microcontrollers are and what can be done with them. Then explain how cheap these are compared to 10 years ago, and make the price comparisons at the end.