Property taxes are based on assessments - the taxing authority's judgement of what your property is worth. In Nassau, it's the county that does the assessing, and Nassau towns and school districts use the county's figures. In Suffolk, each town does its own assessing.
Assessors judge a property's worth on a variety of factors, including surrounding values.
Each year thousands of homeowners seek reductions in their property taxes by trying to show that the assessment is unfair - either because the evaluation is overstated, or because neighbors with similar houses pay lower taxes. Of course, the latter doesn't necessarily prove anything. Sometimes houses on the same street belong to different school, garbage or other special districts, and the taxes will differ even with identical assessments. Those costly details. Let's say you have a legitimate beef.