我們先來看看來外對討價還價這個概念是怎么理解的。

It is not a common practice in Western countries... I have a lot of problems coming to terms with this concept here. It is where you and the seller come from different ends of the price to pay for something. Obviously you want it as cheap as you can and the seller wants to sell it for as much money as they can. It then is a process of negotiating a price that both buyer and seller are willing to accept.

看來討價還價在西方國家不是很常見的呢，但是我們還是要掌握怎么表達。
常見的有: negotiate a reduced price, beat sb down, bargain, haggle…

beat sb down: to persuade someone to reduce a price 說服某人降價，殺價

He wanted $8 000 for the car but I beat him down to $6 000.
他那輛汽車要價8000元，但我壓到了6000元。

Bargain: to discuss the conditions of a sale, agreement etc, for example to try and get a lower price 討價還價，商討條件

He said he wasn’t prepared to bargain.
他說他不愿討價還價。

Haggle: to argue when you are trying to agree about the price of something 講價
通常搭配是: haggle (with sb) (over sth)

I left him in the market haggling over the price of a shirt.
我扔下他自己在市場上就一件襯衫討價還價。