Have a real estate agent write offers for you on properties that you go see with her or him.
If a property was sold for $400,000 at the peak of the market, and you get an offer accepted for $200,000, you are getting a 50% discount from the peak value. It does not matter the house is currently listed for $210,000 or for $ 199,000. - The current list price is not closely correlated to either its current market value or it's historic peak value. The only issue should be "are you getting the house for the lowest price you can get it or a similar house for?"
Nobody today will buy a house for its top value. Though many will sell you a house for half off the old price, no one will sell a house for half of its current value.