Each autumn, the marketplace offers a mirror of what a culture finds delightful, excessive, or both at once — and this season, Costco has held up that mirror in the shape of a five-and-a-half-pound chocolate Frankenstein head. For $54.99, the 'Monster Mash Chocolate' by Ten Acre Gifts arrives with a mallet for smashing it open, inviting consumers to turn the act of eating into a small, sanctioned spectacle. That it sold out almost immediately, and now commands double its price on resale markets, suggests that the appetite for theatrical novelty is as perennial as the holiday itself.