Some "pre-foreclosures" are already listed as short sales on the MLS and may be pending sales, even though they have a notice of default. Others may never get foreclosed on or may be bought at the trustee sale. Some are in the "pre foreclosure" state for a year or more. The "prices" you see have nothing to do with market value and are most often the amount in default and are no reflection of a for sale price.
My advice, just skip over them, unless you intend to buy at Trustee sale, then subscribe to the services.
Best place to search for homes truly active on the market is Metrolistmls.com you will see most of the properties available with the exception of a few for sale by owners or ones listed with agents that don't belong to Metrolist, 2nd choice for searches would be Realtor.com their feed comes directly from the MLS.