I'd list it at 10k. I own one and won't let it go. The owners of 7.3s hold onto them. The ones for sale are usually really beat up... So if yours is in good shape you have a good shot at being paid well for it. As the new 50k diesels come out the older ones look better. No urea fluid or emissions crap to deal with. Shoot, they stopped making the 7.3 because of emissions, that's it. The engines are legendary.