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.