prices will vary depending on the engine (1.8l or 2.0l for petrol, and there's a rare 2.0l HPI version, plus diesel options), trim levels (lower trims like the GLX only have power shutters on the front, moving all the way upto the Executive with the bells and whistles), and how well it's been maintained - certainly worth (as with any euro) paying a premium for a non-abused specimen
haven't been checking prices recently but 1.8 to 1.9 for an executive 2.0l in good condition should be fine.
Harshan should be able to answer this much better as he was 406-hunting for a few months
BTW there's two 406 models, the older d8 and the facelifted d9, I doubt if the d8 fetches anywhere near this kind of money (facelift also included engine change and some other non-cosmetic improvements)
and this is the point where I want to
if you are still in a position where you're trying to decide whether to buy a 406 or a fb14, you are probably going to be better off with the jap econobox. you might as well be asking if you should eat dragonfruit or apples.
please, find a seller who will give you a test drive in a 406 (preferably an executive), drive it around, ask him to demonstrate the options, and make your own judgement first. if the experience to you is just like a fb14, it's no point us telling you any different.
certainly there are factors that are not apparent from a test drive (such as price/availability of parts and mechanics) but it's no point talking about that unless you at least like the car.