Do you want to ask about the difference between paper bags and plastic bags? What is the difference between boxes and plastic barrels?
Paper bags and plastic bags The difference
The paper package is called Tetra Pak. The difference between these two packaging forms will have different requirements for the processing technology. What you call thicker means that the milk packaged in Tetra Pak is fresher. Processing and packaging times are short. The price difference is due to different packaging costs. Tetra Pak's packaging has applied for a patent, and they are the only one to provide this kind of packaging in China, so the price is ridiculously high, and these differences are passed on to consumers.
The difference between boxed and barreled packaging
The two types of packaging are different in processing technology. Most boxed milk requires the addition of stabilizers to extend the shelf life. Bottled milk is generally fresh milk, which uses pasteurization technology and is sterilized instantly. It does not contain additives, but its shelf life is very short. International dairy companies have operated this way for hundreds of years. I don’t know what the production process of domestic dairy products is like.