They can buy and sell at the same rate. However, when currencies float against one another, banks may take a loss on their foreign exchange transactions as they end up buying high and selling low. Capital Risk Financial businesses, especially banks, earn profits by making loans. In the absence of higher interest rate spreads, banks can earn additional profits only by squeezing their net worth accounts to a smaller and smaller percentage of total assets. That leaves the banks with very little cushion to protect against insolvency.
Financial businesses depend upon interest income and have interest expense.
If they have too many fixed rate loans or securities and too many variable rate liabilities when interest rates rise, their profits get squeezed from below by increased interest expense. If they have too many fixed rate liabilities and and too many variable rate assets when interest rates fall, their profits get squeezed from above by lower interest income. These items are called off-balance sheet items. They include standby letters of credit, loan commitments, loan sales, futures and opions contracts, and interest rate swaps. Standby letters of credit are instruments that underwrite finacnial commitments.