If a buyer low-balled me but was otherwise pleasant, I'd just pleasantly decline the offer ... Why get all bothered by it? After all, it was just an offer. And why hang up on him - You probably just burned a bridge. That guy might have wised up & come back to buy at your price after learning more, or changing his mind, or whatever. Once you hang up him, you've increased the chance that he won't come back just because he knows he ticked you off.
That's just the thing- this guy wasn't pleasant...if he did come back with a better offer, I was prepared to tell him that he couldn't buy it from me for any price- I wouldn't sell it to him purely out of principle- Like I said, I don't need to sell it and as others have pointed out, as long as I'm not using it, it isn't costing me anything except storage space.