[pdelbarba]

You're pretty close. Basically they used to be about the price of a nice car, but it become fashionable to sue the pants off everyone who was involved with the manufacture of the airframe if it was involved in a crash, fatal or not. An entire sector of lawyers emerged, taking advantage of lax regulation surrounding liability in the sector. This began at the end of the 70s and the prices skyrocketed to the point where Cessna actually ceased production of the 172 airframe. Congress had to get involved and passed the GA Revitalization Act which, among other things, limited liability duration on airframes. This was enough to cause the 172 to return to production but I've heard that something like half of the total cost of a new 172 is for liability insurance. This become apparent when you start to look at newer designs that have similar price tags and seat counts like the SR-20/22 line. For $330k you get a skyhawk that can barely break 110ktas. For $400k you get a composite Cirrus with better performance than a 182 (the next level up in Cessna's line). It's also possible that the inclusion of the whole airframe parachute system in the Cirrus design was enough to get the insurance companies to give them a little more of a break.

The other big factor is the construction. Cars are largely stamped and then welded together. Aircraft are either stamped/milled aluminum that is then manually riveted together (production volumes are orders of magnitude lower than cars so no robots are used) or they are made of fiberglass/carbon fiber composite which is even more labor intensive to form. The issue with the comparison with cars is that they're way cheaper than they reasonably should be because of the sheer volume that they produce. In the time it takes cessna to build one plane, ford can pump out 1000 new cars.