This card came from eBay recently for what I considered a reasonable price. Many, many similar cards went by in recent years, usually from sellers who saw the name of a HOFer and decided it must be worth the big bucks. Unfortunately, there's not much to a card that could easily be a "caption this cartoon" contest!
An above-average number of GADs end up in PSA slabs, given the high grade you usually find them in. That implies the card maker distributed them in a small area, sold only sets, or stashed them somewhere safe for a while. Even at 45 years old, it's difficult to add much to a card's value when most of the others are in the same shape. No doubt lots of modern collectors run into the same problem when they get cards graded. You're better off hunting down a comparatively rare or nice card before taking the trouble.