Wow. Amazon has a 30 day price guarantee. If they lower their price within 30 days of a purchase, you can just call them up and get it refunded. 1-800-201-7575. Thanks, Fatwallet!
If you want the price of your purchase monitored for you, check out this site. It will compare your purchase price to Amazon's price twice daily and email you if Amazon's price is lower.
Or just use http://www.refundplease.com/ to automatically alert you if the price drops.
Here is a better one: http://www.nukeprice.com
My personal favorite:
http://www.pricealerter.co.uk/
There's a UK and US version too.
If you want the price of your purchase monitored for you, check out this site. It will compare your purchase price to Amazon's price twice daily and email you if Amazon's price is lower.