Please buy this from me I need to get rid of it today!
Okay, I'm interested. Is there anything wrong with this sub?
The only thing wrong with it is that the previous owner was a lying cheating piece of a man. 
Hmm, so you'd say that your judgement might not be so good?
Oh my judgement is just fine. This thing is not welcome in my house anymore. 
Well, if it's that important to get it out of your house fast, I'd be happy to offer $200 right now.
Well probably is the court says I owe him 400 so I need at least for his garbage so I can pay him. 
Well, I think if we work together we can come up with a mutually beneficial arrangement.
Such as?
Well, how about I pick up the subwoofer from you tonight, and I'll pay $300 for it.
That still leaves me 100 short. I really need 400
Well, without some other perks I really can't go any higher than $300.
I'll deliver it to you. And throw him some of his clothes that are hanging around my house. 
What size are the clothes?
Large
Well, okay, if you'll come over here, tonight, with the sub and the clothes, I think we can make a deal at $400.