I have no idea how accurate/up to date those publications were, but I can say for sure that the Overstreet (comic) Price Guide has always notoriously undervalued may key books (hell, may books in general). I know collectors point to prices in the old OPGs and marvel at what an Action 1, Tec 27, or Marvel Comics 1 was worth back in the day. What they don't realize, and what may parallel those movie poster guides, is that the market price was far higher (especially for high grade copies) than what was stated in the guides. Bruce, Rich, and Sean can attest to this