Why do books have a retail price printed on the cover?

Manufactured goods may have a suggested retail price, but that price rarely is printed on the goods themselves or the packaging.

One exception is greeting cards, candles, cosmetic items, etc. that are sold in a chain. For those, it seems that setting an invariant price is ok (because the chain is selling lines that can’t be bought elsewhere) and it eliminates the need to label the price with a tag.

But the book industry is different. Publishers almost always stamp a price somewhere on the book, why?

So the guy at the register knows how much to charge.
Not all booksellers use bar code scanners with UPC code lookups.
Barnes & Noble doesn’t need it, but a guy selling books at an independent small bookstore (rarer than all heck nowadays) or perhaps a magazine stand kind of place does, in fact, have some use for a printed price.

Incidentally, there are tons of books that do NOT have prices anywhere on them.
Books expected to stay ‘in print’ for more than a couple years are likely to have no printed price so that publishers can adjust for inflation. This would be most common among specialty publishers like Butterworth-Heinemann, Routledge and others that do small press runs.
BTW, grab the hardback book closest to you. Look at the back cover of the dust jacket. There will likely be a bar code with numbers above and beneath it. The number beneath will be 13 digits and begin with 978. To the right of that bar code will sometimes be another block of bar code. If there’s a number adjacent to that beginning with a 5, the number following the 5 is the book’s MSRP.

Because author’s royalties are determined by the cover price. A bookseller can discount, but the author doesn’t lose his cut.

In addition, nearly all books are fully returnable for full credit. If the bookstore returns a copy of a book, the publisher wants to credit him the proper amount. Thus, if the price goes up while a book is in print, printing it on the cover (which is returned for credit on paperbacks – hardcovers and trade paperbacks return the entire book, so it’s the same thing) makes sure the bookstore is properly credited. Otherwise, a bookstore might return the books they paid the lower price on and get credit for the higher price.

Of course, now that the US and Canadian dollars are at par, all those books with things like “$7.99 U.S., $10.99 Can.” printed on the cover are starting to cause a bit of friction.

Unless that number is 90000, which is the code for a non-priced book.

ISBNs are sold in blocks. Unfortunately, they must also be translated into barcodes in blocks. That often results in small publishers getting barcodes for ISBNs not yet assigned to a specific book or priced. The 90000 code allows for a unique barcode number to which pricing can be set at a later time.

As for the OP, RealityChuck’s explanation is the best reason for the practice, except for the “that’s the way we’ve always done it” that’s always a good answer when it comes to publishing.

Also, regardless of whether books have the price printed on them or not, all books have a publisher’s list price, which is the MSRP. The way books are sold to bookstores is as a discount of the list price. Sometimes it’s only 10% (usually smaller publishers) sometimes as much as 40 or 50%. But all books must have a list price so when a publisher makes a sale, they know that the wholesale price is X-33%, for example. Why they do it that way, I dunno. But they do.