Step 1: Understand the context of the question
The question is asking about the basis for determining the buying and selling prices in foreign exchange (forex).

Step 2: Identify the key terms involved
The key terms are 买入价 (buying price) and 卖出价 (selling price) in the context of forex.

Step 3: Recall the definitions of buying and selling prices in forex
In forex, the buying price (bid price) is the price at which a bank or financial institution is willing to buy a currency, while the selling price (ask or offer price) is the price at which they are willing to sell.

Step 4: Determine the basis for the buying and selling prices
The buying and selling prices are determined from the perspective of the bank or financial institution、The price at which they buy currency from you (the customer) is the buying price (or bid price), and the price at which they sell currency to you is the selling price (or ask price).

Step 5: Relate this understanding to the question
The question is asking for the basis or reference point for these prices、The buying and selling prices are quoted from the bank's perspective.

Step 6: Conclude the basis for the buying and selling prices
The buying price is the rate at which the bank buys foreign currency from the customer, and the selling price is the rate at which the bank sells foreign currency to the customer.

The final answer is: 银行角度.