Of course, some pricy books from the last few decades are expensive because very few people expected them to go up in value (think: Newsstand editions, reprints, preview books, etc.). DC spec has been dead for some time, so I wouldn't be surprised if they put together a good slot of movies and people start paying a lot more attention to the books. That said, it'll probably only be key first appearances that really end up being worth the storage space (assuming you're only holding onto them for the potential of price appreciation, and not because you want them in your collection).