If you paid $249 for a 16GB Nexus 7 on or after October 14th, you can receive a refund of the difference between the new ($199) and old ($249) prices. From Google
Price Protection for devices on Google Play
If we reduce the price of a device on Google Play, we'll refund the difference in price if your purchase occurred within 15 days of said price reduction.
To be eligible, requests for a price protection refund must be submitted within 15 days of the price reduction occurring.
Nexus 7 (16GB version only) purchases from Devices on Google Play are currently eligible for Price Protection if the purchase was made on or after October 14, 2012. If your purchase is eligible, we'll refund the difference in price within 14 days of your request.
There is a link on the above-referenced web page to request a price difference refund.