Well, if you were to trade it in to a music store, they'd probably give you 50% of what it cost brand new. So, you could split the difference between 50% and 100%. I'd recommend knocking off 25%, take some pics, and post it. Someone gets a fair deal, and you get more than you would have on a trade.
It's tax return season, and those are rare and beautiful. I bet you'll sell it quickly. Good Luck!