There are two main reasons why very expensive down jackets are classified as Category C:

1. The quality factors of the down jackets. Expensive down jackets often use high-quality raw materials, such as better fabrics and higher-quality fillings, which increase the cost of the product. In addition, the delicate handling and technical requirements in the production process will also lead to higher costs.

2. Product classification standards. In clothing classification, Category C refers to clothing that cannot directly contact the skin, and down jackets are generally classified as Category C. This is mainly because the down in down jackets can easily irritate the skin, and the standard GB 5296.4-2012 "Consumer Instructions for Use of Textiles and Clothing" stipulates that clothing that directly contacts the skin should meet Class A standards. Therefore, in order to comply with this regulation, some high-quality down jackets may be classified as Category C.

Please note that this does not mean that all category C down jackets are necessarily expensive, because the price is also affected by factors such as brand, design, processing, etc.