There could be many reasons for this happening. The strength of the offer could be a big reason. Contingencies, inspections, and bank roll could all play factors. An example would be how much money does a specific buyer have in his bank account. A buyer that has millions of dollars is considered a much stronger buyer. As an agent, we try to get the best offer and the highest isn't always the best offer. Let's say a short sale went on the market for 250k. Buyer A makes an offer for 250 and only shows 255k in the bank. Buyer B makes an offer for 245k but shows a million in the bank. Sometimes short sales can take up to 6 months to close. Buyer B is a better offer to go with because he will most likely have that amount 6 months down the road. I say this because as a listing agent, this example has happened to me. I had to find another buyer 4 months later because the original buyer did not feel comfortable spending all of their money on one property. I would say 20,000 is a big difference though.