当需要回复外贸邮件已经是最低价时，可以采取以下策略：

礼貌回复：首先，要礼貌地回复客户，表达对他们的关注和感谢。可以表示很高兴收到他们的邮件，并表示尊重他们的询问。

解释情况：在回复中，可以详细解释为什么已经是最低价。这可能是因为公司政策、市场竞争或其他因素导致的。通过解释情况，可以让客户更好地理解为什么价格无法再降低。

提供价值：除了解释情况外，还可以提供其他价值或优惠来吸引客户。例如，可以提供免费样品、优先发货、优质的客户服务等。这些额外的价值可以弥补价格稍高的缺陷，并增强客户的购买意愿。

引导客户：如果客户仍然对价格有疑虑，可以尝试引导他们关注产品的品质、品牌、使用体验等方面。这些方面的优势可以突出产品的价值，并让客户意识到价格并不是唯一的考虑因素。

保持沟通：在回复中，可以表达愿意与客户保持沟通的意愿。如果客户有任何疑问或需要进一步的信息，可以随时联系。这样可以建立良好的客户关系，并提高客户的信任度。

以下是一个示例回复：

Dear [Customer Name],

Thank you for your inquiry regarding our product prices. We appreciate your interest in our products and services.

We have already provided you with our lowest possible price. Our prices are set based on various factors such as our cost of production, market conditions, and competition in the industry. We strive to offer competitive pricing while maintaining the highest quality products and services.

However, we understand that price may be a concern for you. To offset the slightly higher price, we can offer you free samples of our product, priority shipping, and excellent customer service throughout the purchase process. We believe these additional benefits will demonstrate our commitment to providing value to our customers.

Please note that the price we offer is only one aspect of the decision-making process. If you are still concerned about the price, we would be happy to guide you through other aspects of our products and services that may have been less familiar to you. We are confident that you will appreciate the quality, brand reputation, and user experience our products offer.

We value your business and would be happy to answer any further questions you may have. Please do not hesitate to contact us if you need any additional information or have further concerns. We look forward to the opportunity to work with you.

Best regards,

[Your Name]