When selling a series of books online, is it more profitable to sell them individually or as a set?

I guess this could go for any sort of thing that comes in a series/set, like DVDs, CDs, etc.

I have a bunch of graphic novels that I don’t read anymore and I’d like to sell them on eBay. Will there be much of a difference in my profits if I sell them as a complete set, or as individual books?

In one case I also have a DVD to go along with the full series of graphic novels. Should I sell the DVD along with the books or as a separate item, and just allow combined shipping?

Thanks everyone. :)