Many supermarkets have this kind of jewelry counter, which sells mostly jade (because the price of jade is opaque, few people know it). Usually, the clerk at the jewelry counter at the supermarket exit will tell you that you can have a lucky draw when you buy something, so everyone who goes to the lucky draw will get a discount prize, which will only be useful if you buy something at their counter. The purpose of changing everything is to make you buy its things. This is a sales promotion method.
As for the goods, they are generally not fakes, but they are not much better. Wool comes from sheep, which is a typical high price and low discount.
High-end jewelry brands will not be set up in supermarkets for the sake of image. Usually in large shopping malls or specialty stores.