Many times when a value is determined for a property prior to Listing it, Freddie Mac obtains two values one form the listing agent and one from another Real Estate firm which is called a BPO, if they are within 25% of each other, then Freddie Mac will in most cases use a value somewhere in between. However, if they are more than 25% off, then they go to an auto valuation model like Zillow which is UNABLE to account for windows, kitchen, etc. So, if you have a house with many issue worth 50k, but the valuation model says homes are worth 90-130k, then they will start out high for the first 30 days, then start dropping price accordingly. Listing agent should prodive very good pictures to suport what he or she think s the public thinks the home is worth and what the real market value should be. I hope that hhelps.