Because at this time you need to sell foreign currency to the bank and exchange it for local currency, for the bank, it is to buy your foreign currency, so the exchange rate is the bank's buying price, not the selling price.

When you need to change foreign currency from the bank, change the foreign currency into local currency, and the exchange rate provided by the bank is the selling price of the bank.

This is the most basic knowledge of foreign exchange, and general foreign exchange books should explain what is the bank's buying price and what is the bank's selling price.

The buying price of the bank is lower than the selling price of the bank.

For example, the exchange rate of RMB against the US dollar announced by the Bank of China is 6.8234-6.8237, the former is the buying price and the latter is the selling price.

We can also think about it from another angle: in order to maximize profits, banks will definitely buy low and sell high.

Therefore, when a bank buys your foreign currency, it will definitely exchange it with a relatively low bank buying exchange rate. At the same time, when you need to buy foreign currency from the bank, the bank will definitely exchange it with a relatively high bank selling exchange rate.

A little wordy