its all a matter of what people are willing to pay for a car. a car that is worth 12,000 and listed at 20,000 probably wount sell if the buyer knows wht the car is worth. I wouldnt take a listing price as what cars are actually selling for, people ask outragous prices for cars all the time but that doesnt mean that they sell them for that much.
Some people are willing to pay huge amounts for cars that arnt worth what they paid mainly because those high dollar ones are big name brand cars like Boyd Coddington, or OCC motorcycles, or a rare make and model ('63 T-bar coupe for example), etc when they could get the same car built for half of what they paid. Its all about bragging rights and form over function.
personally, I am for function and drag racing and would rather spend money on something that will make my car faster then something that will make it look better. so I would never over-pay for a performance part since you can order them in a catalogue which is very buyer-friendly but apperarance items can be one-off custom pieces that are seller-friendly since they can exadurate how much time and effort they have into a certain item to jack up the price. its hard to sell a drag car that has 12k in parts for 20k but its much easier to sell a one-off show car that has 12k in parts/labor for 20k.
sorry, not sure where Im going with this, just my 2cents on the issue.