We've already had this discussion here, but since it's an ongoing topic of concern to writers it's no surprise to run into it again. Alison Kent discusses new versus used books here.

No author would ever expect a reader to go hungry or be unable to put gas in her car or run short on day care dollars in order to buy new books. Not at all. That’s just not practical, and we authors living contract to contract are nothing if not frugally practical ourselves. As Vanessa Jaye says in the post I’m about to link to, a reader’s budget concerns will always trump an author’s need for earnings – as well it should! (And no one here is telling anyone else what to do. This is about consumer education, and consumers understand this.)