If you conduct a search in the AED, you will see a group of buttons just above your results (or look at the image on this page). There are 6 buttons and 2 blue "records found" links. Here is what each of them does.
Get Current Estimate - this button actually accesses two services, Get Current Estimate and Probability of Reappearance. What you do here is select those records that are of interest (or all) and then click the "Get Current Estimate" button. The database will then calculate an estimate of the current value of each one (as far back as 1914). It does this by factoring the overall appreciation (or depreciation) in the value of books for each year since the date it was sold, based on the millions of records in the AED. By calculating current value of older prices in "book dollars" it enables you to make sense of older records, and better estimate the likely current value of books that do not come up for sale often. In the case of sales made in euros and pounds over the past 15 years, it converts these to U.S. dollars.
It also provides an average estimate for all of the records you select. Obviously, for this to make sense, you need to select only copies of the same book and edition. This will smooth out aberrations in price where a sufficient number of records is available.
The other service provided under this button is Probability of Reappearance. This looks at records going back 50 years and estimates roughly how often the book you have selected can be expected to come up at auction. For this calculation, you need to select all similar items, that is same book, same edition. This knowledge can be very useful in knowing how aggressively to pursue a particular book. You might choose to pursue a book a bit harder that only comes up about once every 15 years than one that regularly shows up every year.
Add to MatchMaker - MatchMaker is the AE service that allows you to select either fields of collecting (keywords) or specific titles or authors for automated daily searching for copies for sale. Once a day, MatchMaker will search AE's database of upcoming auction listings, as well as AE's Books For Sale, eBay, AbeBooks, and other sites. The next morning, it gives you a list of new matches (that is, only newly listed books, not a repeat of the listings you received the day before). Non-subscribers to the AED have access to MatchMaker for auction and Books For Sale listings, but not for eBay, Abe and others. Trying to conduct manual searches of the various sites daily for all of the keywords or titles you follow is practically impossible, meaning you may miss opportunities you have spent years searching for. Not with MatchMaker. Here is a more detailed description of this service: click here.