Keepa (https://chrome.google.com/webstore/detail/keepa-amazon-price-tracke/neebplgakaahbhdphmkckjjcegoiijjo https://chrome.google.com/webstore/detail/keepa-amaz

Keepa (https://chrome.google.com/webstore/detail/keepa-amazon-price-tracke/neebplgakaahbhdphmkckjjcegoiijjo https://chrome.google.com/webstore/detail/keepa-amazon-price...) is a Chrome plugin that shows you the historical price of any product, injected into the Amazon page. I use it all the time!