I’ve spoken about this issue of “irrational pricing” a couple of times before.
www.elitefourum.com/t/irrational-card-pricing/24401/1
Looking at the price of a PSA 10 1st edition Koga’s Beedrill, this can be seen as an inevitable correction of a price that was too low compared to the other low pop cards in the set.
According to pokemonprice.com, previously Koga’s Beedrill has been selling for under $200 through 2018 before selling for $266 in August.
Meanwhile, Giovanni’s Persian had been selling consistently for over $400, but there is no public sales data for that card since July 2018.
And Misty’s Golduck is an interesting case. Previously, the card had been selling for around $300. But there was no public sale of the card in over a year until the card sold for $775 in August ( cgi.ebay.com/ws/eBayISAPI.dll?ViewItemVersion&item=223460083351 )
Considering Koga’s Beedrill, Giovanni’s Persian, and Misty’s Golduck are almost entirely valued for the fact that they are needed to complete the set, the price of Koga’s Beedrill clearly didn’t make much sense compared to the other rare cards in this set.
This just shows the inherent value of set cards that have a much lower population report than other cards in the set. They are far harder for people who want to have complete sets to find so people are willing to pay a lot more for them when these cards become available. This is why Chansey sells for 3 or 4 times as much compared to some other PSA 10 1st edition base set holos.
So if I had to guess what will happen, Koga’s Beedrill will settle at a significantly lower price than what it sold for in this instance but also a much higher price than what it had been selling for previously.