somewhere in between what you are willing to pay and the owner thinks they are worth? Ever watch "Pawn Stars"?
IMHO, it's a black cork football with a machine carved head, regardless if George Soule ran the duplicating machine or somebody else. Current price on a Bean decoy is $66 if you buy three or more. Retail markup means it cost around $33 to make. Black cork, head, paint, let's call it $12 for materials. That leaves $21 for a person's labor and bennies.......probably about one hour for somebody making $12/hr.
If there is such a thing as "collector value" for a George Soule Bean decoy they are worth what you are willing to pay based on condition I guess. Not just a Bean thing, I scratch my head at what people pay for Mason decoys.
If it's something that you are going to gun over they probably need repair/repaint and I'd say $20-$25, given that to pay for the materials to make a tan cork decoy with a cedar or basswood head, eyes, paint, etc is gonna cost you $25-$30 plus your time, probably way more than an hour.
If they are going to cost you $75 apiece, buy some decoys from George Williams or Pitboss or any of a multitude of contemporary decoy makers who make Bean decoys look somewhat.......impressionistic.