I think that's actually just the crown on an upward trend - this may be the new value for the item. Another one sold for $91 (3149032464) and another is currently at $76 (2958368345). Granted, all relatively-new collectors, but precedent is being set too consistently here for it to be a fluke. (3148525277 sold low at $41, without documentation.)
Ironically, the Wizards' policy of printing ESD/PDF files through SVGames may be the culprit here - this is an item that won't cheapen in value (or be made affordable) by a simple print-out re-release. WotC has never shown any indication of this item being republished.
As an aside, that may be what started the whole
H1 "price fixing" frenzy this year - the module has enough individual pieces to it that even casual collectors greatly value a real copy, over the $4.74 ESD. From customer feedback, I know there's a similar mentality behind B10 and X10 as well.
