The seller mentions that the back is blank, plus it's a scored card so I'm 99% sure it's from the Lost Wacky S1 set.
On a similar note I can't believe how many singles from those Lost Wacky sets are selling for high amounts. I don't get the mentality of buying that set one at a time. Maybe some buyers only want a handful of titles from the set. My guess is that they are uneducated buyers who don't know the origin of the various Lost Wackys and jump on any that they see. It's understandable since it can be very confusing and there is little about them on the internet.
I agree, I think it's a combination of lack of knowledge & lack of availability. If a set is broken up & sold separately, the chances of getting all the cards are pretty small. Given those circumstances, I think people are purchasing a card or 2 (or more) of the ones they like from what's available - the alternative being not having any.
I raised the issue about the signed red veins card because I recently purchased a red veins poster signed in black ink. Oddly, it came with a red veins white back card (unsigned). I thought it was a lost wacky thrown in for good measure, so I gave it no extra thought. Now seeing the signed red veins card, it made me think it might have been a different release with the poster. From what I researched about a year or more ago, the red veins posters signed in black were given out at comic con, and the ones signed in red were given out privately by Strephon.