Well show a list of all the parts, whether bought new or used and the price paid for each, but since you used it for a week all parts are used. Then if are you selling with it loaded, list what OS and any other software. Thats the only way someone could even give you a solid answer. And don't forget most won't buy without seeing first.
Now you know you why you didn't get the answer your were looking for and if a price shows up that you use don't forget the commission, 10% at least for doing your work.