I’m not sure when this picture was taken exactly, but I think the Poliwag winner shared it just before he started listing some of his copies on YJ, which sold for 1-2k USD each. This was back in 2016 (since the SNAP thread/post that contains this picture was created in May 2016 and last edited in December 2016). He still had 4 left in January 2017 according to this post, after an Efour member met the winner in person to buy one of the remaining five copies. I’m pretty sure the winner either sold all his copies (or all minus one to keep perhaps?) in 2016/2017.
After that they’ve switched from owners a few times, and Poliwag is the most likely to pop up for sale on eBay and alike because of these sales in 2016/2017. In comparison, the Magikarp has yet to pop up for sale even once in all these years, and the Pikachu was available for sale for the first time I’m aware of mid last year for 330k USD - which was taken down eventually (before I had time to bundle a max available mortgage of my own and my little brother’s /s 
).
The other eight SNAP cards have all sold a couple of times, and there is one SNAP collector in the US UK who owns all eight I believe (below a picture of seven of them, missing the Gyarados which I think he bought later - and you can also see the Gyarados in our very own Gyarados Graphical Wizard @shizzlemetimbers 's collection thread: www.elitefourum.com/t/shizzlemetimbers-collection-2022-6-years-in-the-making/13665/162 
):
Greetz,
Quuador