It depends on where are you going to buy these. For sweaters, you'd better bring one at least, for you need to wear just get off the plane. Buy silk; suggest you go to Xiushui Street(https://www.travelchinaguide.com/cityguides/beijing/shopping/xiushui-street/) . You can buy clothes in Xiushui too, it is half price than department stores. Do you want silk fabric, clothes or carpet? No matter what, you can find there. So, you can try your best to negotiate with the price. Here is some more info about Beijing Shopping(https://www.travelchinaguide.com/cityguides/beijing/shopping.htm) .