This is just my thought. I think it is just like konoha tree and this along with the time limited shop would help the big spenders to get naruto nine tails chakra fragments. For normally putting coupons it doesnt break even because the redeem points are too far away as Garv mentioned. Also the drop rates of stamina potion and the blocks with less than 50 coupon value are too high. I dont have proper statistics of this, but I was not ready to go get it after my first 10 draws turned out to be a disaster. Probably they should work on these drop rates to make it more profitable event. One thing i have noticed is first draw has a high chance of being a good reward.