The only cars that have a definitive price attached to them are new cars i.e. cars that are all the same new condition, spec, availability etc etc.
Anything else is like houses, you base your asking price on spec, condition, availability and how quick you want to sell it.
Most people want to make money of course and their ability to do that will depend on the buyer i.e. an unknown quantity at the time of initial 'advert'.
Auctions are an interesting place to go to get a 'handle' on what you think something will sell for and what somebody pays on the day. Not many people sell houses at auctions only the ones that need work and that's often the case with cars but not always.
I sell things at what I consider is a fair price and I don't usually have to wait long eg. 350Z, 240Z track car, 370Z, 240Z recently.
IMO there are not many Datsuns that are worth more than £30k but people do pay more so am I right or them? I consider my current blue car is worth £35k (rust-free shell, very good spec) however I would advertise it at £40k just in case I was wrong, so I don't blame anyone for trying. The buyer sets the price being realistic, not the seller.
