I have just updated my Amazon Device Buyer’s Guide in time for Prime Day tomorrow. While considering all the Prime Day sales that are already live or coming soon, use the buyer’s guide to determine how good the deal is relative to past sales. The guide lists an “Okay,” “Good,” and “Great” price for nearly every device Amazon makes including Fire TVs, Echos, Fire Tablets, and Kindles. A “Great” price represents the lowest price the device has ever been or is expected to be, based on previous Prime Day and Black Friday sales. The buyer’s guide also lists when each device was released and how often Amazon updates each device, to help you get a sense of when a device is overdue for an update.