There are added factors when the bank owns an unoccupied house. Insuring an unoccupied house is riskier and more costly and thus there may be exclusions such as for vandalism and copper theft. Also banks hire companies to maintain the houses and that cost is just adds to the loss.Market values are set by the sale of like kind real estate in the area over the past several years. Cost and value are not equal.
The value of a neighborhood is assesed by many variables, including good schools, good municipality bond ratings, good fire protection, good infrastructure, etc. It takes lots of ingrediets to mix a good cake.
If the copper is stolen, the cost to replace it can be a substantial part of even a low value house. With the high risk of problems, plus winter heating costs, the banks know a loser when they see it and sell at a low price. This creates a downward spiral effect that can be quite rapid, hence the $15-40k sales prices we are seeing in FLOMO and surrounding areas.