Not all the properties showing on RealtyTrac are foreclosed. Many of them are on that list because the property owners have received a Notice of Default and later, a Notice of Trustee Sale.
When property owners are in distress and miss their mortgage payments, or are delinquent in their taxes after so many months, they are served the notice of default. At that point of time, they have several options to cure that default: forbearance, reinstatement, loan modification. And if they have no choice but to walk away, they may list the house for sale as a short sale.
BUT! The price that you see on RealtyTrac is not necessarily the price they will list it for.
If they are unable to sell the house as a short sale (very long process, and very difficult to get approval if there is more than one lender, and nearly impossible if there are different lenders), then the owner can surrender the property via deed in lieu of foreclosure, or file for bankruptcy.
Before a foreclosure, the owner may be served a Notice of Trustee Sale (and this will also be picked up by RealtyTrac) where it will be posted for bid at the county courthouse on a certain date. If no one bids, then the ownership reverts to the lender.
2-3 months after the foreclosure, the lender's asset manager will engage a realtor from among a list of REO (real estate owned) agents who will market it for sale at, close to, or below market price.
Bottom line: what you see on RealtyTrac as the price is NOT the price it will list for. That number that you see is more than likely the amount of delinquency.
If you're interested in finding foreclosures that are already offered for sale, engage a realtor to find these properties for you. You realtor can uncover relevant information that may be helpful to you in submitting and negotiating your offer.