Hello
We have to talk more before that, or this will not work. 
ok. what is your asking price
It is 170, but I am willing to lower it. It is in good condition, but it is used.
how about 100.00
100 is a good deal. But, I am feeling charitable today, so I can lower it more than that.
really? how about 85.00?
85 is a good deal too. But, I will give it to you for 70, since that is what you initially offered. Does that sound good?
yes. but why the back and forth then?
Because we have to converse about it to make a deal.