Just as comics are a specialized group of collectibles, so are books. Some books are not sold for their content but for the age, condition and perceived value. Really old books can be in a condition less than pristine but intact. Other books are valued for their rareity. Others their history. and still others for their signature. Then the books that are First Edition, hardcovers, softcovers. These are usually wanted for their content, their story if you will. You will find lots of different prices . Also graded as to condition. If they are for collection you want the top grades. If just for reading then the grades do not need to be graded as well. Sometimes sellers price the books really cheap for an attention getter for their store. Others stock them in their store. You will find many different prices for the same title and condition. So it is not necessarily true when you as a seller are listing the book that you will agree with the average price ebay gives you. It could be an average of one or an average of many. You be the judge. With the original cost of books going up so too the cost of used books does follow. If your books are in nice condition and a subject that is interesting and wanted then price them as what you think is fair to you and buyer.