The data is purporting to show total property value, not land value. Thus, a residential tower with 400 units at $100,000 each and occupying five acres adds $40 million to the valuation. In contrast, a five-acre spread with a single mansion might only be worth $5 million. Thus, a county with more residential towers will have a higher aggregate value than a county with more luxury mansions, even though the former is much more affordable.