I paid 14,500 for a 2005 LX470 w/ 135k miles from a private dealer, great condition chassis for year (minimal-to-no-rust), and only non-disclosed "gotchas" so far have been Levinson-related (and fixed at low cost by me), poor maintenance on AHC, and fasteners in poorer condition than I expected after my initial visual inspection.
Based on NADA/KBB, I did ok. Dealer was a nice guy, low pressure, and gave me all the time in the world to look over the vehicle.
Don't feel like I stole the car, nor feel "taken." I'm gonna get crucified for this, but me thinks the guys that say "pay what it's worth to you" are usually the same guys who beat up a seller, detail the car, then hope they can convince you to line their pockets w/ a few grand. I've seen it several times on ExPo, and those guys make me sick. Used car dealers are one thing..they have an overhead, have to make a living,and are expected to ge...ummm,..usually a bit less tha forthcoming. But..guys who are ostensibly kindred aficianados who buy low/sell high on enthusiast sites? Got no use for that, personally...
Sounds like I'm attacking the guus in this thread who stated that... I'm not. I haven't been here long enough to see it happen here. A couple guys on ExPo..well...they make me sick and embarassed to be a human.
My relatively un-informed short answer? 8k, maybe 9k if it's beautiful, well maintained, records, timing belt/water pump done, etc.