I've opened a sealed box of each set from Base-Neo Destiny, and received 12 holos in each box (aside from Destiny, in which I pulled 9 holos and 4 Shinings). I believe PikachewTofu is correct -- each Wizards set was labeled something like "odds of receiving a premium foil card 1:3"; pulling anything less from a box was just bad luck. But yeah, it was true even for Base-Gym 2.