I could never sell it for this much. Is my home over-valued?

The value we assign to a home is based upon a study of sales of comparable homes occurring over the prior 3 years (For 2017, we looked at 2014, 2015 and 2016 sales). These sales must also all be valid, non-foreclosure situations. What homes are selling for in the current year have no effect on the market value assigned for tax purposes.