The Creature Catalogue was meant to be a softcover, but they accidentally printed it as a hardcover. They chose not to increase the advertised price, and so we got an extremely cheap hardcover.
Mind you, I'm not surprised at all that prices are increasing: I'm not sure that sales are all that hot, and the US economy is *not* in a good place.
Yup. Not to mention that introductory products are often priced artificially low. The D&D core rulebooks are often less expensive (per page) than other hard covers of their size . . . and I'm sure it's the same with the softcover Essentials products.
But, then again, I've heard people suspiciously complaining about rising prices since I started hanging out here on ENWorld roughly 10 years ago. It's called inflation folks, deal with it.