I have a lot of authors on my ereaderIQ watch list for the specific purpose of replacing physical copies for a good price. I need to clear some shelf space somehow, and since I prefer to read ebooks now (mostly so I can change font size for my aging eyes!
) I find it is worth doing even if I'm not actively reading a book or series. I'll also replace books for full price if I'm in the middle of rereading a series.
There are a handful of authors that I am keeping physical copies either because it is a unique edition or signed, or just some of my favorite authors (Jordan, Heinlein, Burroughs, Kurtz and Eddings, Tolkien etc).