AV Cable: ~$10
AC Power adapter: ~$40
Halo 3: ~$20
GTA4: ~$20
These are the prices from Gamestop. These are all prices of pre-owned equipment. Note that Halo 3 will drastically lower in price once Halo: Reach comes out in 5 days. The point if you selling it is to get more money than what you would from Gamestop will still giving him a better deal than what he would at Gamestop. I would suggest around $70.