Dealing with syllabus error as instructor I hope it will be forgiven that I am going the anonymous-coward route when asking this question.
I am teaching two courses this semester.  My university has been mandating lots of evolving changes to syllabi, so I tried to organise my syllabi so that I could make changes to both in one place, rather than having to do lots of cut-and-pasting.  (Basically, lots of \includes in a TeX file.)  Somewhere along the way, I messed up which parts were common and which parts were course specific, and I listed the same textbook for both classes.
Classes start Monday.  The bookstore listings have been available for quite some time, though I don't know how long.  I made the class syllabi available yesterday.  Today, a student wrote me and asked about the conflict between the syllabus and the bookstore's listing.  I immediately fixed the error and sent out a class-wide announcement.
Unfortunately, it turned out that a student had already purchased the wrong book.  I don't know if this student purchased the book through the official bookstore (which might be eligible for return), or from Amazon, or somewhere else.  (I have reached out to check, but I want to have some idea of how to proceed regardless of what the student answers.)  I also don't know if this student is the only one affected.
If the student cannot return the textbook, then they have suffered for acting in good faith on information that I presented that they could not really have known was wrong.  I therefore feel the burden of dealing with that suffering is on me.  However, I am not sure how to proceed.  The easiest answer—in the sense of easiest to say, and to justify—is that I should reimburse the student (and I have checked with my dean that I am allowed to do this).  However, the book is $300 new (a footnote here, about how little I as a professor am aware of the cost of the books I assign), and there are 30 students in the class, and I cannot afford to commit to this option without knowing how many students are affected.  Is there any other ethical way to proceed?
(Another option that has been suggested to me is to suggest that the student sell the book, and then reimburse them for the difference.  This would at least defray some of the costs for me, but I am not sure if it is ethical for me to put that burden on the student.)
Well, you are polite enough to care about this deeply. I think one of your students might be polite enough to help you. As I understand, this &quot;wrong&quot; book actually is the course material in one of your other classes. You can ask in that class if someone who hasn't bought the book would like to buy that spare copy. You can incentivize it with a discount on the brand new book (something like 25 dollars) and you can pay the small difference to the student.