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 got great pulls when i got my first Shining Legends Elite Trainer Box. A Hyper Raichu, Zoroark GX, and Shining Jirachi. When the set first came out. Those paid for most of the box. My point is, that sometimes Trainer Boxes from Special Sets, such as GEN/SHL have a higher pull rate than the pin collections. Plus you get a cool exclusive promo out of getting the mini-set Trainer Boxes.
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.