I've actually been following this book in the lower, raw grades on eBay. High grade copies aside, the lower raw copies appear to sell surprisingly well also compared to other Batman keys.
My opinion, I think most real collectors know that this book should not be more significant to the other Bronze keys, but the fact of the matter is, it definitely is right now. I don't see this changing any time soon. For better or for worse, I've found that this book gets a lot of outside press that makes it the unofficial representative or "face" of when Bats returned to his gothic roots, even though it was not this exact issue that started the trend away from camp. What I mean by outside press is that this cover has been showned or mentioned in numberous articles about either Batman or O'Neil/Adams, Levitz's giant "75 Years of DC comics" has a full page spread showcasing this cover, HBO's "The Pych. of Batman" used this cover in the program when discussing his dark roots. This program was latered included in the movie DVD, creating yet even more exposure. There's a few other references as well, but I can't think of them off the top of my head right now. What I'm trying to say is, as long as this book keeps getting advertised like this, people will always want it.