The main reasons why milk is cheap in summer are as follows:

1. Xiajin Milk has its own cattle raising base, and the cost is relatively low, so the price is relatively cheap.

2. Xiajin milk is a low-priced product, which is positioned in the mass consumer market, so the price is relatively low.

3. Xiajin milk has adopted a more efficient operation mode in production and sales, thus reducing the cost and making the price more competitive.

In a word, Xiajin milk is cheap because a series of effective measures have been taken in production, cost and sales, making the price relatively close to the people.