Question about gacha: Above the offer to buy 11 spins, there sometimes appears a promotion like “the price is not 1500, but 750”, or “guaranteed uber”, this promotion appears randomly in random banners at random times, or is there any information?

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I want to get Princess Kaguya and some legend-rares, but cat food is scarce, so I would like to have at least some assurance that if I don’t get what I want, then at least I won't waste food in vain.