What is the meaning of "Room to haggle" in negotiation?

I only know just what haggle means. but it is a phrases

As far as I know, it isn't an idiom. It simply means that there is plenty of room (space) for negotiation. For example, if you go to Istanbul (where bargaining is traditional) and you want to buy a pen, the vendor might say that it costs $30. There's plenty of room to haggle there, as the pen most certainly isn't that valuable, and the vendor knows it - actually, they expect you to haggle.