Have you noticed that there are different banners in the Pack Store? Do you know what they represent?
☆ Purple banner with a chest and magic lamp: get the maximum bang for your buck! You can only buy this once!
☆ Purple banner with stars and a crescent moon: a worthwhile purchase that's better than regular packs at every price tier! You can only buy a limited number of these each time they're in stock!
☆ Plain red banner: packs as ordinary as the banner, but there's no purchase limit so you can keep buying them whenever you need!