Selected feedback comments left for the OP's buyer:

• "The item is all used but advertised as new, seller isn't trustworthy"
• "Game arrived damaged.. did not appear to be a new game, seller uncooperative"
• "I bought a New but I receive a opened game. I had no solution."
• "Picture was false if i saw the true pic i would not of bought it!"
• "Item NOT new as listed. Had to go to Paypal to get partial refund."
• "Game was advertised as brand new but showed signs of wear and tape over seal."
• "The dlc codes were already redeemed seller hasnt resolved" (Item advertised as NEW)
• "The collectible map/poster inside was damaged but other than that it was fine." (Item advertised as NEW)
• "never received,harrassing messages from seller due to "not received" dispute"
• "fast delivery,price was good,but can't recommend seller many issues on ethics"
• "can not recommend,bad ethics and requests more money??angry seller I think"
• "Took too long and not as described" (Item advertised as NEW)

OP's buyer would appear to be buying used games and reselling as new - there's definitely an ethics issue here as others have speculated - OP, I'm sorry but you've encountered a bad apple here.

I feel sorry for people who have to deal with this crook - they're definitely not getting the best deals in Australia.