Would you consider a volume discount?
批量购进可以再优惠吗？
If you buy 1000 or more, you'll get a 10% discount.
如果您能购进1000件以上我们就可以优惠10%。
Could I have a lower price?
可以给我便宜点吗？
Could you give me a discount?
能给我个折扣吗？
How about buy one and get one free?
买一送一怎么样？