The rule of thumb is that a fully reconstructed salvage car is worth roughly 60 percent of a car of the same make, model and year with a clean title. So when buying a reconstructed car, start with the Kelley Blue Book or National Automobile Dealers Association (NADA) value and multiply by 0.6. Is the asking price higher or lower? If lower, it's a good deal.
But this formula takes for granted that all the damage has been repaired, and this very well might not be the case. If you're buying a salvage car that hasn't yet been repaired — or a car that's been repaired, but not to 100 percent of its full condition — deduct the predicted cost of these repairs from the 0.6-times-the-Kelley Blue Book value.