Well considering I'm one of those two, and I had never heard of the series until I played VIII and IX randomly on Playstation + earlier this year and really enjoyed them.  I suppose I could have done a little research and looked up the sales of past titles in the series, still the more sales the better.

It's below Monstrum Nox on just PS4 though, even though it had the Switch to help out this time around. So I wouldn't really say selling less than the previous entry is a success, when the installbase that can play those games is larger.

I've got no skin in the game, but isn't Ys VIII much higher than 40 009 just from looking at the chart you posted?
PS Vita 47,681 + PS4 30,764 + Switch 6,817 + PS4 super price 2,428 = 87,690
And Ys IX sold 45,378 (PS4) + 7,324 (Switch) = 52,702.
I don't know what kind of numbers Ys X needs to be a success, but from the chart you've presented it looks to have declining sales for its opening weeks.

Top 30 software posted. Even more new games!

Companies really like to steal Playstation players in Japan. It's the only country where games are consistently more expensive, why is FIFA 2800 more expensive on PS5?

MK8DX now at 5.5M!!! Quite an accomplishment after 6 years since release.

Because it's normal for PS5 games to cost more than Switch games. In Europe EA Sports FC24 costs €80 on the PS5 and XSX, €60 on Switch (all prices are MSRP).

3rd party software sales aren't as bad as it seems when digital is accounted for. PC is a big platform in Japan now, it's safe to say that some games sell about as well on it as they do on Playstation.

Also the survey (30k voters) estimates below sound about right, give or take 5%:

I get this question a lot, and while I can't give a full answer, there's at least some info available.

On the most recent CESA white paper, they held a poll to see what the retail/digital split was, and for 2022 they had

Overall 30%
PS5: 35%
PS4 50%
SWI 23% https://t.co/cu3eZ9qYf2 pic.twitter.com/P9BUZpiRfX

— Game Data Library (@GameDataLibrary) October 5, 2023

PS4 having a higher digital ratio is a standard thing for older platforms. When Switch gets replaced, its digital ratios will also gradually climb. PS5 is behind PS4 here despite the Digital Edition, but it's probably well ahead launch aligned (35%~ vs about 15% iirc).

Physical declines are misleading.

I said ENOUGH !

Say it's success and that's it.

The problem here is that this charts combines all SKUS for Ys X but not for the others.

According to it, Lacrimosa of Dana did around 85k between PS4, Vita, and Switch. Granted, those didn't all launch simultaneously I believe, but it's misleading not to compare just Vita sales of one to PS4/PS5/Switch of another.

Not saying Ys X flopped mind you, just that its numbers feel lukewarm.