Hi, I am interested in your headphones
Great I'm asking $150
Is that price negotiable?
Sure I'll come off a little so make an offer and I'll let you know. They have only been used twice and are really nice.
That's awesome. $75 cash? I can also pick them up from your house today and pay cash or venmo you the money now. 
I'm afraid you a bit low; half off for like new condition hurts.
What did you originally pay?
I paid $150 for them and I only used them on to flights and put them away.
If the headphones cost the same price brand new, then I'll just do that then. I'll pay $100, final offer
Agreed, you got a good deal at $100. Thanks