You shouldn't be paying more for each pack to "guarantee" pulls. That goes against the premise of packs. It still works out at like $10 a booster and most of those packs only end up having a single $1 holo anyway and maybe a useful Trainer/reverse. And most of the Promos are either useless or reprints. I think the best pull I've had from a 4-pack box is like, 1 holo and 1 regular art EX. It came nowhere near covering what I actually paid. The only time I'm actually tempted to buy those types of boxes is if the promo/figure is really good or if it's on sale.