I don't consider those two items a fair comparison (HORNS vs. L&K). First, I put more stock in a novel collectible than a comic book collectible. But that aside: I already have all the comic books, and as much as I love them, I am not willing to pay $265 for a hardcover collection of only a few of them - despite the signatures. There are still multiple S/L volumes to be released of this story, so the all-in cost of the complete story (in S/L format) is going to be pretty significant.
HORNS, on the other hand, is a complete novel. Pay once and you get the whole thing. $330 may be a bit high in today's market, but I don't think it's completely unreasonable given the author's popularity, the limitation figure (200 vs. 500 or 1500, etc.), and the fact that it is a novel, not a comic book.