I think Sergio is right, that sale ended up with a huge profit for the seller but this is not typical. I bought mine used about two years ago from a mate here on the boards and at the time I paid $180 USD. I had to immediately replace the battery as the 8 year old unit would only hold a charge for an hour or so. It actually still functions well today.
Very nice little player only unit, no doubt one of the coolest Sony made in my opinion.
Be honest about the battery when you list it, most serious buyers for this unit will know the details of the design and understand that the small, non-user replaceable LiON battery has a shelf life of around 5 or six years. May I also suggest that you try to get a few nicely lit focused photos of the unit? The aesthetics of this cool little machine will go a long way to stir up interest in buyers, that can't be appreciated with grainy, out of focus pictures ...
Let us know when you list it, I'd be interested in watching it to see what you fetch!
One other thought I had is that it seems like the market driven sales always do better and the idea is to sell the unit, too many greedy folks will list a unit such as this for Buy it now at $250 or something way too high and bidders don't want to immediately commit to that, start the bidding at zero or some low and reasonable value, no more than $50 and you'll see what the demand is. I see units all the time sell for a good and fair market driven price when listed this way. Other units listed with high BIN or high reserve prices will just come back up for sale again because no one bites ...