Wow, you really are a rookie ...
Once, I appraised a shopping center that was under contract. No matter what I did, I was coming in about a million over the contract, about 25% in that case. After looking at it every which way I could, I asked the buyer about it. His response? "Oh, I let the seller of the center hide 50 subdivision lots in my name when he was getting divorced. He's just paying me back." The sale closed at the contract level, with the sale price recorded in public record data.
Sound like a good comp to you?