It can be said that there is no black market for foreign exchange in Hong Kong, because there are many foreign exchange outlets, all of which are legally operated. Unlike the mainland, it is legal to exchange foreign exchange with banks. However, the foreign exchange outlets in Hong Kong are quite dark, giving full play to the Chinese nation's specialty of bullying the market (in China, a clothing vendor can charge different people 100! )。 They look at people and give prices. If you don't ask a few more questions, they will kill you severely. The black market in Chinese mainland is illegal and there are not many market opportunities. So the price is reasonable. Basically the same. It won't make much difference. Just a suggestion: you'd better change it on the mainland.