When we bought our home, I had a professional appraiser give me a replacement cost and I had a friend who was a custom home builder give me an estimate. My HO insurer hired an outside firm to do an inside/outside valuation. All three were within $10,000 of each other, so I felt pretty confident about it.
Then I changed insurers and they had a third party do a valuation. He was there maybe 30 minutes. The year before, the inspection took at least 90 minutes. The value this time came in $100,000 more and was based in part on an understated square footage, wrong number of bathrooms, etc.
Moral: Garbage In, Garbage Out
