This is the advert for my car, for which I paid the asking price.
Alfa Romeo : Alfa 159 TI 2.4 JTDM 20V Q4 (remapped)
The reason that I paid the asking price was because it had full history with a recent main dealer service, nearly new tyres and was in excellent condition inside and out, just a couple of superficial scratches and a couple of stone chips on the bonnet, 10 months MOT and 4 months VED. Also because it was a 210 (possibly more as it's been re-mapped) and the tyre wear issue has hopefully been addressed.. It is a private sale, so no dealer come back if it was a pig in a poke! A bit of a gamble there.
I had been looking for about 3 months just to get a feel for what was a sensible price for 159s, and had only seen one 2.4 Q4 which IIRC was at Veloces, 57 plate can't remember the milage but price was £15,500, which was out of my budget for a three year old car.
I had concluded that I would probably not see a 159 Q4 diesel that I could afford based on Velloces asking price, and had resigned to run my then present car until this spring and then buy a "standard" 2.4 diesel, then my 159 2.4 Q4 came up for sale as did another two within days of me commiting to buy this one, one was Red and the other was Grey.
So to answer your question, I saw 1 X Q4 at Velloces, then another two (plus mine) just after I had paid my deposit for my car, and this was over a period of about three months. So they are fairly uncommon.
Will this affect your decision?