我看得不是很明白,如果楼主的意思是:附件里的单价就是调整后的5月份的价格的话,可以这样翻译:
We adjusted prices in May due to cost increase of raw material.
Enclosed ( Attached) is the up to date price list for your reference.
So sorry for any inconvenience caused.
如果不是上面的理解的话,直译如下:
We made come changes of prices due to cost increase of raw material.Pls kindly check attachment.
What's more,our price will be adjusted again in May.So sorry for the inconvenience it caused.