Amazon launched Pricy , a plugin that allows you to know the price history of a specific product and thus have a new parameter before making a purchase.
Since there are products that constantly go up and down in price, this system helps to make a smart purchase by detecting if the amount to pay promoted as an offer is such.
Pricy comes for Chrome, Safari, and Firefox. Just by positioning with the mouse it will give the price history and will suggest if it is time to buy the chosen product or if it is convenient to wait for another better moment.
Another possibility that Pricy offers is to configure a notification and thus find out when the chosen product is at a certain price (established in the same notification by the potential buyer) or below.
Ideal to provide customer satisfaction with each purchase.