Look at the pictures of the house and tell me it is estate quality in any way. It looks modest and mundane at best.
There are about 50 homes on the market around him and only 2 recent sales as shown by Zillow. All the other homes on the market are roughly 200K and below. The recent sales are about 110K and 60K. The 90K comp is about 2500 sq ft. HIs house isnt 5 1/2 times as big. Its not even twice the size.
There is also such a thing as over improving a property for a neighborhood and not getting your money back.