Similarly, it is definitely cheaper to buy gems in Brazil than in China.
If it is expensive in Brazil, there are several reasons:
(1) Shops where tour guides earn kickbacks
(2) A store that specializes in receiving foreign tourists
(3) High-grade gem shops, etc.
You can tell your friends: If you come to Sao Paulo, you can go to several Japanese shops in Libertad. Fine workmanship, reasonable price, cash payment with 10% discount. You can't buy fakes in such a store. Note: Don't buy gem jewelry with price preference in small shops or markets.
Personal experience: The jade necklace and earrings I gave my family last time cost 200 baht (equivalent to about 600 RMB), which was very beautiful. Good luck. .