The other day I had a chat with the guys of one of the soundtrack shops and they said that even a world premiere release of a score by, say, Delerue does not sell well any longer.
I think you underestimate the buyers who will trot these out (marked up, of course) at all kinds of con's. At those events the disposable income is flowing like water.
I don't underestimate anything, as I've done these kinds of titles before - they've all done okay because they were Les Baxter or Dana Kaproff or Albert Glasser. Bill Marx? Uh uh, and it's a different market today. If what you were saying was true, then When a Stranger Calls would have sold out long ago. That was Holy Grail time for so many here, if you read those posts, and then it sold okay but we've been sitting on two hundred of them for ages now.
I don't disagree but my experience has shown me that horror collectors can be counted on if they know about it. Yorga has a huge cult following and you can never completely write off those collectors.