I noticed something similar a couple of weeks ago that VS across the board got a lot more expensive.
Furthermore, Gengar cards in general completely skyrocketed in the last 1.5 years. So Mortys Gengar is the combination of a set that went up a lot and a Pokémon which cards went up a lot. Still crazy to me when you think for how much these cards went 1 or 2 years ago.
There was also a good discussion, with @Cerulean making a good point that VS stayed stable for the longest time and with it being Japanese exclusive & the great art of the set, it is not that surprising that it got more expensive.
I still think that at least for some cards those extreme price jumps are not sustainable and that there at least in for some correction in the future however I doubt as well that they will ever be as low as they were in 2023/2024.