Dear
Due to the increase in raw material costs, we must unfortunately raise the
cost of our merchandise to you.
We have avoided raising our prices for as long as possible, but we can no
longer prolong the inevitable. We have enclosed our new price list for your
review which goes into effect on [date] Any orders placed between now and [date
of increase] will be honored at the lower prices.
We wish to thank you for your valued account and know that you will
understand the necessity for this price increase.
-商务英语
daiy