This is a discount price这已经是打过折的价钱了

今天的几个句子是有关购物的：I'd like my money back, please. 请把钱退给我吧。2.Would you give me a discount? 能再便宜一些吗？3.Could you exchange this, please? 您能给我换一下这个吗？4.Could you tell me how much it is? 您能告诉我多少钱吗？