What gives with the 1964 Topps' Curt Flood?

I have been trying to pick off vintage cards, more commons than anything-or minor stars, from our Redbirds' Topps needs list. I started noticing that Curt Flood's 1964 Topps #103 was more expensive than other lower series cards.

Yes, Curt was a pioneer in Baseball for helping rid baseball of the reserve clause. However, he wasn't a superstar. So I couldn't figure out why this card would, eventually when I do pick it up, cost nearly $20. So the last couple of evenings while watching the Birds play I have been scrolling through stories on Sports Collectors Daily and came across not one but two articles on this same issue. Here, is the most relevant of the two articles Curt Flood. Well this article led me to this article on Espn's website Cornering the market. I am not going to rewrite the article but I think the picture below sums it up best. Yes, he has 4,000 of these f&%#@&$ cards!