No longer are the days that Amazon would honor you a partial refund if the price of the item drops within a week of purchasing it. The only cases where the partial refund will still be offered is with TVs sold from the online retailer. This news came about with to price-tracking services and customers posting on Reddit. There were a bunch of online services that would automatically contact Amazon on your behalf in case there was a price drop within a reasonable amount of time soon after purchase. These services are what likely have made Amazon change its mind about such...
Source: http://www.gsmarena.com/amazon_will_no_longer_honor_refunds_for_dropped_price_after_purchase-news-18373.php
