Condos going to court auction (Legal Execution Department) and properties that banks sell after foreclosure (NPA, published on PropertyHub). Each one is compared with the median asking price per m² of its building, or of its district when the building has too few listings.
Auction starting prices are the court's appraisal for round 1; if nobody bids, later rounds may start lower. Bank prices change often. Always check the unit, its title and any occupants before bidding: auction sales are as-is. Areas include the balcony when the court lists it. Court appraisals tend to be low and many units are in older buildings, so a big gap against a district median (which includes new buildings) is not the same as a bargain; the building median, when there is one, is the better guide.