U won't exchange if you know the poor term. U can exchange even hk has no such style.
If the wallet costs hkd 7000 and in Paris hkd4600, ended up u can only exchange 4300 worth of goods, because the buy and sell spread rate they use is wide. I helped my sis bought a bag in london she didn't quite like, wanted to change, in London is hkd17500, in hk hkd 21400. Chanel only allowed her to exchange 16400 worth of products. So ended up she kept the bag.