Late response, but...
Yeah, no. Considering you can't even get dressblooms normally on DMM, it doesn't make sense for them to be that cheap here either. Drip is correct.
At most, they've sold gold dressblooms for $30 and rainbow dressblooms for $50 at certain times. The last time they had that offer though, they dropped the latter's price to $40.
So that deal was indeed -70% off. Whether or not you agree with it is a different matter, but it was a consistent price, unlike some other Nutaku sales.