Always valued at fair market value minus debt. Unlike collectibles (see Baseball Cards) price guides are less misleading in attempting to define a value. Most all such guides employ two numbers, one listed as "retail" or "dealer" price and the other listed as a "trade in" or "wholesale" price.

My inclination has always been to use the "wholesale" value, where this is the more likely transaction result for an individual attempting to dispose of his or her car and conservative numbers generally make more sense (anyway) where most vehicles are unlikely to be sold. My preference of price guides is the Kelley Blue Book (a free resource) over the Internet. There are many useful "paper" and Internet guides, including the "Edmunds" booklets (and Internet service) and others. I don’t know if one of these services is "more accurate" than any other but the Kelley’s listings have seemed to predominate (as a matter of quantity of use) in my cases.

See also Leased Vehicles and Business Cars.