在面试时，如果你想用英语表达“土豆价格”，可以采用以下几种方式：
直接表达：
- “The price of potatoes.”
- “How much do potatoes cost?”
在具体情境中表达：
- “I’m interested in the current price of potatoes.”
- “Could you provide information on the pricing for potatoes?”
询问价格变化：
- “Have the prices for potatoes increased or decreased recently?”
- “What has been the trend in potato prices?”
询问特定地点的价格：
- “What is the price of potatoes at this store?”
- “How much do potatoes cost in your local market?”
在商务或市场分析中的表达：
- “According to the market report, the price of potatoes has been fluctuating.”
- “In the agricultural sector, the potato prices have been a significant factor.”
在回答问题时：
- “The price of potatoes is around $2 per kilogram.”
- “Currently, the going rate for potatoes is approximately $1.50 per pound.”
根据具体的对话情境，你可以选择最合适的表达方式。记住，在面试中，清晰和准确的表达是关键。