3x2

It is very usual to see in many food stores (local shops, supermarkets...) promotions such as buy two get another one for free. Of course this atracts costumers, but that is not the only point of it. Lets say you are doing your weekly shopping and when you buy cookies you find out there is
a 3x2, great! Each week you keep purchasing the same cookies and taking advantage on the discount, by doing this your are generating a need of 3 packs of cookies per week. The problem is that ,eventually, the discount will finish and you will still have the generated need of 3 packs instead of two, so you will have to buy 3 packs and pay all of them.