The main reason is foreign exchange cash, not physical paper money. Theoretically, banks need to invest in the storage, security and transportation of funds. And cash, digital bookkeeping, and even hundreds of millions of Juck Zhang films don't need such a big space to store. Moreover, the cost of foreign remittance is also very low, which is the change of digital bookkeeping. Cash, the bank cost is low, so the purchase price is high.