For example, the cost problem often mentioned in economics is often seen in milk and coke. Cost is a problem that everyone who develops the economy will consider. After all, cost is an essential expenditure, and it is impossible to develop the economy without cost. In milk and cola, milk is generally carried in cartons. Coke is generally sold in plastic bottles. From this point, we can see that although the two drinks are often drunk in daily life, the packaging they use is really different. On the one hand, milk is basically white, and people don't need to see its color. Moreover, it is cheaper to use paper boxes. Coke is a kind of soda, which itself is to stimulate people's taste buds, so using transparent plastic bottles can make people see its color and arouse people's appetite. And the composition of plastic bottles is really not high. Moreover, from an economic point of view, when you invent and study a product, you should not only consider the cost, but also consider whether the user is convenient. Coke, as a drink that can be drunk everywhere, is actually easy to carry, so it is designed as a bottle, which can be put in the bag at will, and it is more convenient to drink. If coke is designed to be packed in a carton, it will actually occupy a large volume, and the weight of the carton itself will be heavier than that of a plastic bottle. Therefore, it is convenient for consumers to sell coke in bottles, and it will also make consumers more comfortable to use it. In addition, the way of storage is also a point to be considered in economics. After all, the way of storage is generally considered in selling this kind of beverage. Milk is packed in paper boxes, which is convenient for cold storage, but if coke is packed in paper boxes, it can be refrigerated, but it is not as easy to freeze as plastic bottles. Coke is delicious only if it is iced.