Two questions:
Something I have a hard time conceding is why someone would buy an item and then sell it for a huge loss, sometimes half price. We all see it often. In an item's description it reads "bought new from authorized dealer, unopened and unused, still in package" or "less than a week old". Another thing I have a hard time fathoming is why sellers who can afford a $5000 CD player don't take an actual picture of the item.

if it sounds too good to be true, it probably is

New and unopened, hmm, I don't want to wait til I get home to find out what's in the box unless it comes from a place with a return policy. Last time I checked, most peeps advertising the way you describe (on Craigslist for example) won't want to know you once your money is in their hand

That's funny you should mention that...

http://cosprings.craigslist.org/ele/1094727972.html

Now goto Amazon and gander at the price new...

Some sellers don't seem to read their email. It's pretty difficult to get an answer to simple questions like item condition, packaging and picture of BOTH units for sale. There seems to be a habit of showing one but keeping the other paired item a mystery.
Sigh

I'd say things like you describe are one of two scenarios.

1. Stolen items

2. Scams