Simple answer, thats how its always been. Oasis rarely changes the price of a ninja.

hes mystery is skill is op dealing critcal means much plus he does critical damage with 1.5x damage

this means he does criticl damage with increased power of 50 % but....if ugive him buffs like increasing ninjutsu 40% it will increase damage in different method 1.5x1.4=2.1 so instead of getting 1.9 he gets 2.1 if u give him 110 nin buff he gets 1.5x2.1=3.15 buff so instead of getting 160 more damage on mystery he gets 215% more

also that 1.5x crit means he doesnt scale with injury as its fixed by the number. thats why its important to break him, since he doesnt get large crit bonus but he can scale with injury dealing some nice damage.

Hit through dodge with mystery, nin immunity, Super armor, Cold-blood scaling, a lot of attributes (which you can buff him in many different way)

Even without the skillbooks, super rares in events has always been priced that high. It it also like this in the China server.

Well what does that make summer and sailor sakura? Are they not super rares? Because they were just given away after is spent over 40k coupons on them!

Not mad, though.

Susanoo draws on the user's chakra in large amounts so long as it is active tellthebell.

The Sakuras are Event ninjas, which are different from Super Rare treasure ninjas.

Also if you spent 20k each on those two, you got scammed madly or went for them in RNG event. Overall, if you spent 40k on these two ninjas then thats on you and not anyone else.

Im guessing it's because of his passive being immune to pure ninjutsu damage? — a perfect tank against Kakuzu online.

As a super rare in Kage treasure Sasuke [Susano'o] is not actually meant to be directly available in events. Theoretically costing 1000 Seal Scroll Sasuke [Susano'o] should cost about 125,000 ingots/coupons by default. For his time Sasuke [Susano'o] was basically a monster that did absurd damage and had super armour. As time went on a key fault was shown, the extra bonus on his mystery turned out to be detrimental. The 75% critical hit and 1.5x base critical damage in turn made him deal next to no damage.

Because his cut scene looks better than rinnegan sasuke

Because he's a super rare in a treasure ._. simple as that tbh plus he has great sb/st