Where are you guys doing the math saying it costs 20k ignots for cursed hidan??
It's roughly about 15 points in two rolls, which is 7.5 points per roll on average.
You need 60 points for one fragment.
60/7.5 = 8
8 x 20 coup per roll = 160 coupons a frag.
160 x 80 = 12800
You can be unlucky, but it's around 13k - 15k.