如何应对客人提降价

事情是这样的：今天一早收到客人要求降价的邮件：

The discount we seek from you (like all other suppliers) is due to the change in currency exchange value. From current situation the currency exchange is strongly in your favour. Therefore it does not matter how much is the shipment/order value since the price of the product should go down in USD. I am sure you understand the concept behind this. All our other suppliers have already agreed on this 6% discount since they all understand the technicality behind this.

客人以人民币贬值为由，要求我们降价6%，并且还搬出其他供应商来，说他们都同意了降价。

问题是，单看汇率，也就是6.35和6.15的区别，最多也就才有3个点，客户要求的是6个点的折扣!

这个价格本来报的时候客人死命砍价，已经降了不少没多少利润了，还想着年底涨价呢，结果他现在反而还要求我们降价。

我们不情愿给客人降价，但问题在于，这是先发货后付款的，我们怕客人先斩后奏扣我们钱。

我在想，如果跟客人解释人工和成本的问题估计说不通，客人肯定会说为何一开始可以做？我一说降价你就这么说？

但是如果降价又心不甘情不愿。各位朋友有没有什么高见呢？