如果价格真的不能再低了.
Dear ，
It's really very appreciated to receive your e-mail.
But It's our best price because of Increasing of material price and labour pay, which make the cost go up. To maintain a quality assurance, our price is very reasonable and in the most favorable.
We suggest that we can do some adjustment of part of material to meet your ideal price.
Please kindly find the attached quotation which is available for your reference.
Contact me if you have any questions.
Best regards.