Too many people try to determine whether a property is a "bargain" by reference to (a) the percentage below asking price it sells for or (b) the percentage drop in price since the peak of the bubble.
Because the peak price was irrational and the current asking price could be irrational, these are not good indicators of long-term value.
Look instead to what a similar property is selling for in a similar sized city where property prices have tracked inflation, or try to figure out how much you would expect an occupant of that house to earn, and figure out the value by reference to a reasonable multiple of their salary (say, x 4 plus a deposit of, say, 10%)
Or take the estimated annual rent the house would generate and figure out what you'd need to pay for it to generate a yield of, say, 6% on the purchase price.