This house actually hasn't sold since 2006 when the current owners purchased it for $805,000 from the builder. Trefry Lane is a beautiful development of very high end homes in Stow. There have been two sales in the development in the past year , one for $710,000 and a second one for $740,000. Appraisers use the must current sales they can within one year but ideally within 6 months to appraise a property. Given that, right now they would probably only use the $740,000. There are very few sales above $700,000 in Stow and depending on the appraiser, they may also go to Acton and Boxborough as abutting towns to gain more comparable properties to use. You can never be sure what a property will appraise for exactly as every appraiser is different despite using a strict set of guidelines.
I would be happy to give you more information and/or come out to the property to help you get closer to a number. It is impossible to guess without access to the house and upgrade records.
Keller Williams Realty Boston NW