A familiar and popular favourite elevenses or tea-time snack, sold in a retail carton in this instance. There are 90 individual twin-finger packs in this bundle - a lot of Kit Kat, so you have to be a fan. It could also stock out a coffee stall, tuck shop or any similar enterprise for an event or even normal daily(?) business.
In this instance, it was a Daily Deal offered at a lower than normal price.