Dealers and auction houses typically base their valuation of books using intrinsic values. Intrinsic value is determined using auction and sales records which reflect actual sales prices. Obviously, auction records are the best way to determine a book's intrinsic value if the goal is to sell the book in less than 6 months. Most dealers have access to auction records that the average person may not have (typically by subscription).
Also, books fluctuate in value. So, knowledge of current market conditions is also needed to attach intrinsic value to any book. Intrinsic value is the value we use in determining the amount we pay for your book(s).
Retail values are the prices the average consumer will find by searching dealer listings online or elsewhere. Retail values for books are siginificantly higher than intrinsic value.
These prices reflect the dealer's costs. A dealer's expenses range from "articles of antiquity" insurance, taxes, employees, and advertisting, to operating stores and websites such as this one. Retail prices also reflect a dealer's patience and how much they paid for the book. Dealers often wait many years for the right buyer to come along who requires that one particular book they are selling.
If a collector wants a particular book, then retail is often the only way to obtain it. Auction houses are the better deal, but the particular book that the collector wants may never show up at an auction. Many rare books show up at auction only a few times over a period of several decades. Even if a particular book is offered at auction, there is no promise that the collector will win that auction.
Retail prices are what a dealer, with a good reputation and client base, can expect to get for their book after waiting many months or years. If you are not a dealer and you want to sell books within a reasonable time-frame with no expense or trouble, then retail prices will never reflect the amount of money you can expect to receive for your books.
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