I think they are and have always been optimistic.
Check this..
http://www.carsales.com.au/all-cars/...d=12035222DFD0
Red Book says:
Average Private Price+ $118,300 - $126,800
Trade In Price Guide+ $104,700 - $113,200
In this case one would hope they are conservative, cause this is a bargain! the car would have been ~$180k otr new... I'm not selling mine for a while, going on these figures.
I have owned and sold both cars mentioned above, Cooper S and Liberty GT, took a big hit on both also. I have learnt my lesson (not really cause I bought the M), stay away from niche cars (or expensive ones like Ms) cause in the end you will loose out.
Good luck selling yours.