Banks charge a certain exchange fee for the exchange between foreign currency and local currency and between foreign currency and foreign currency. Moreover, banks charge according to the "cash buying price" rather than the "foreign exchange selling price". The price of the former is much lower than the price of the latter, and depositors will suffer certain losses, and sometimes exchange losses will even exceed the difference income of interest.

Since RMB is not freely convertible under capital account at present, it should not be easily convertible when the income from RMB exchange is less than that from direct foreign currency deposit.

It is not worth the loss to convert RMB into foreign currency and deposit it in the bank on the black market. Some foreign currencies do not have the interest rate and strong exchange rate of RMB at all; Black market foreign exchange prices are high, and counterfeit money is risky.