[john70t]

"Sale price through a third-party Realtor(tm)" = "Arm's length transaction" = "Fair market value"

The fair basis upon which taxation should occur.

Even if your area doesn't have caps, and is dynamic, the one across the street should have been re-assessed.
That is favoritism, discrimination, and fraud.

Get a real-estate lawyer. Get an independent appraisal or two.
Do a LOT of research for past sales nearby.
I had to go to from local board of review to state tax tribunal level three times to get fair taxation.
One involved an expensive lawyer. It paid for itself within two years.

A thousand fleas upon local tax boards.
I will pay $1M over the next 40 years for two small houses..owned over a decade
Yeah. I did the math.

Does anyone wonder why rents are so high? That's why!