It means sellers sell their with high price, buyers need to lower price, so both sides need to come to an agreement about money.Therefore, bargain does not mean niggard.

• 但是，讨价还价就是指，卖主的东西太高，买主们需要降低价钱，所以需要和卖主们达成协议，因此，讨价还价不等于小气鬼。