property owner is free to value his own property at hatever price he chooses. It is incumbent on the municipality for purposes of taxation to either agree or disagree and if they disagree to submit their own judgement as to value. The property owner can either accept the municipality evaluation or dispute it via a legal action.
The same thing holds when applying for a loan. In that case it is the lending institution which has the final say re the property value for purposes of it’s worth as collateral.
I’ve been through this process all the way to the Appeals Court where I won.