Because it is necessary to buy foreign exchange from the bank to pay for the goods when importing, it is calculated according to the foreign exchange selling price of the bank. When exporting, it is calculated by the foreign exchange payment sold to the bank, so it is calculated by the purchase price.

This calculation method is actually the same as doing business with a trading company, buying goods and then selling them. Of course, the price is low when you buy it and high when you sell it. Otherwise, all trading companies will close down.