More than likely they are just the prices sold back to the bank, redfin culls the data from the recorders office. When you see a map of redfin sold homes (or any other website that does the same thing) and the price is silly high or silly low, just check the sales history for clues. If there is a recorded sale in 2006 for 600k and a recent sale for 640k, while the comps are 300k, that’s the trustee sale back to the bank, it still records like any other sale. Sometimes it’s a silly low price because multiple lenders were involved but they don’t total them for the recording and it’s not always the highest that is picked up by the data sites. If you see a 2006 600k sale on the history and a 550k sale from early 2009 and then a 300k sale last month, that is not a bad flipper, that’s the bank taking it back for the amount owed in january and then the new buyer for a more more market based price of 300k.
Sold means the owner changed, it does not always mean that it was sold on the open market, but any good repo stalker knows, those are the ones in the “on deck” circle.