Part of the appraiser's job is to exclude sales, not just include sales. The excluded sales are those with atypical terms or motivations, to the point where it affected price either far below or far above what we refer to as "market value" ..and market value only happens at the terms defined in the market value definition used in the appraisal. The MV def describes what the TYPICALLY motivated buyer would pay, for a property reasonably exposed to open market. This property was not listed or offered to anyone else thus had no exposure to the open market Buyer had atypical motivations who vastly overpaid, result is the buyer did not act prudently. Acting prudently is in the MV definition, but it's not sexy so appraisers tend to overlook it. Even if this buyer was smart or well informed/ well advised, they chose to overpay for personal reasons, thus did not act prudently.
J - Thank you for your thorough response. "act prudently" is the phrase I was looking for. I've just about finished writing this puppy and "act prudently" is going to be the cherry on top of the sundae! Happy Tuesday.