https://www.pcgamer.com/inside-collectors-edition-costs-375-and-contains-something-made-by-sex-doll-manufacturer-realdoll/

iam8bit has revealed a collector's edition of Playdead's dark and disturbing adventure game Inside, though 'revealed' may not be the best word since there's very little indication of what you receive for the stated price of $375. We know it comes with a disc copy of Inside for the PS4, as well as Steam codes for both Inside and Limbo that you receive via email after purchasing. As for what else it might include that costs so much ("Other stuff" is how the site puts it), they won't say. However, they've partnered with Realdoll, so we can at least speculate.

Realdoll is a company makes life-sized sex dolls with PVC skeletons, steel joints, and silicone flesh. If you've played Inside (and finished it), you probably noticed there's a rather fleshy thing in it. So, it stands to reason that the Inside collector's edition may include a fleshy replica of the fleshy thing, but iam8bit isn't saying and apparently won't say until it actually ships.