Lucky stars has always been rigged, nothing new. Some random f2p will get one or 2 tendo frags to give everyone the illusion of randomness, but I can garantee you that "paying players" will not get anything unless they reach the predetermined "breakpoint" where enough money was paid to aquire the prize.

I'll add to my previous message to make it very clear. Do not spend a single coupon on this event if you have spent money on this game, unless you intend to get 450 stars, nothing less! This event is not random, it is full of "breakpoints" where you need to reach a certain amount of coupon/ingot spent before getting anything. Do not expect 2-3 Tendo pain shards to just pop out randomly if you do 30-40 spins.