That aircraft, and every other is worth very precisely what someone is willing to pay for it.
Yes, be guided by the sticker in the window or whatever, but remember that manufacturers are not selling, even though they are discounting heavily, therefore the used market is depressed both in value and volume, and there are bargains to be had.
Get your pre-buy done properly (pm me if you'd like some help with how to do that), and be diligent throughout any purchase, but when deciding how much to offer, focus on what you're willing to pay for the aircraft in front of you, not on the number in it's window...
Good luck, the Falcon is a nice machine!