A good price is whatever someone is willing to pay. If I had any spare money laying around, I would make you an offer because I would like to add a 996XT to my station. Unfortunately, this is one of my "broke" seasons.
If you list it at that price, you'll likely sell it quickly. As long as it's in good condition, that is. Leave yourself some negotiating room and be sure to list what accessories are with it and if you still have the box. Products with the box seem to sell for more than those without.
Trust them for what? I've listed scanners there, but don't think I've sold one through them. I've had more luck with a local scanner forum, but not ever area has them.
Check prices on Ebay for used scanners. In particular, look at used scanners for sale by individuals, not companies. You can also look at Craigslist, but they don't seem to have a lot of scanners listed.