Why are Korean cosmetics on Taobao cheaper than those in duty-free shops?

Fake, Korean duty-free shops are also fake, and more rich people are cheated. Shops that don't accept Koreans at the door are all selling fakes. If Koreans complain about buying fakes, the shops are mainly sentenced, so these fake shops do not accept Korean natives. In a country where everyone has a fake face, can you expect to sell you the real thing? Not to mention Taobao.