Only a handful of copies exist of each, probably less than a dozen known copies of each issue in any condition.
Jun 2015: Comic Book Postal Auctions - a Very Fine Minus copy of #17 described as 'Bright fresh covers, cream pages, slight creasing to 2 interior pages. Only a few copies known to exist' fetched £1,003. A Very Fine Minus #18 described as 'Bright fresh covers with some slight ink dust residue, cream pages' fetched £958. A Fine Plus #19 described as 'Bright, fresh covers 2mm trim to RH cover edge, cream pages' fetched £1,277. A #20 in Very Fine described as 'Bright, fresh covers, cream pages' fetched £1,390.