Both Google and Asus had announced a price protection system for customers who purchased the Nexus 7 during a specific period of time, before the drop in price for the Nexus 7.
For Asus, they will be offering a 25 pounds refund for UK customers who purchased the Nexus 7 (16GB) directly form Google or Asus before October 29 last month. Google on the other hand, will be offering a $50 refund for U.S. customers who purchased the Nexus 7 after on and after October 14. To check if you qualify for the refund, you can visit Asus or Google website for their respective terms and conditions.