I'm a Real Estate guy, so I have to chime in.
We always say Fair market value is what a knowledgeable, willing, and unpressured buyer would probably pay to a knowledgeable, willing, and unpressured seller in the market.
In every market, and at anytime, there is always a pressured Buyer or Seller somewhere. That's why no rule is 100%, but is true most of the time.
As a Seller, if you find the price too low, don't sell. As a Buyer, if you find the price too high, don't buy.
It's the pressure factor that makes the difference, and that's hard to quantitate.