导购口语:

Prices have up to twenty percent off. Do not miss the chance.
8折优惠，不要错过机会。
We give you a discount of 20% since we're renewing our inventory.
我们因为在出清存货，所以商品八折出售。
Opening sales at preferential prices, all goods 20% off.
开张大酬宾，所有商品八折优惠。

语句解析:

give sb. a discount=offer sb. a discount （主语）给某人打折扣。
give sb. a discount of 20% 给予某人八折优惠，也可以说give sb. a 20% discount。Give sb. a discount on sth. 给予某人某物的折扣。

情景再现:

The mall is giving a 20% discount on some brand-name clothes.
商场正在进行名牌服装八折优惠活动。
Since you are our regular customer, I could make a concession.
由于你是我们的熟客，我可以给你优惠。