I bought 120 dices at 2400 coupon
Which I got 101+ medium thread out of (that's how many I exchanged, and I still had 7 dice left over, too lazy to roll individually for now), which is valued at 3838 coupon

Granted, i feel I'm getting less magatama, but I'm not 100% sure. Stlll, even if I did, this is a far better discount than anything else, the medium thread alone makes it worth it.