Many titles heavily reduced in price. If you've just got a PS4 for christmas and need to stock up on games, buy more than one to offset the shipping price and save more.
Examples:
Driveclub 25GBP
Evil Within 22GBP
Alien Isolation 22GBP
Wolfenstein 16GBP
Infamous SS Preowned 17GBP
I feel that the way games depreciate in value quickly that it is better off having less, or at least buying less at a time and only when you are going to use it.