Ok so this is a deal I saw at EB Games.
Increase your percentage by adding extra trade ins:
2 x Games = 10%
4 x Games = 20%
8 x Games = 50%
Ok now for the tricky part, L.A Noire at EB is priced at $108 however at JB it's priced at $78. L.A Noire is valued at $64 as a trade in from EB. So now do the math:
Purchase 8 copies from JB at a total price of $624
Trade in the games at EB at $64 a pop add your 50% bonus which then equals to a total amount of $768.00
Go Bananas and spend that credit on whatever you want. You could even go back and do it again or better yet get EB to price match and repeat the process. Not sure who can be bothered to do this but thought i'd throw it up on here anyways.
http://www.ebgames.com.au/search?title=L.A.+Noire
http://www.jbhifi.com.au/games/la-noire/
NOTE: I have not tried this so don't blame me if it doesn't work. Just a heads on the trade in specials they current have.
EB Games are so over priced that the extra trade credit doesn't mean much