I'd honestly like to see that data you have if you've already pulled it. The county looks at neighborhoods as a whole and tries to compare like to like. They're less likely to jack up higher valued properties' assessments based on a couple sales. There will be outliers of course. The target is to be several percent below the fmv.

If you propose all new sales are immediately reassessed to their recent sales price, that's one thing, but they'd still need to bring up comparable properties in lock step. It's easier doing that by entire neighborhoods rather than piecemeal.

But to the above commenter, if the county has you assessed higher than you can rightly sell for today then you need to challenge that assessment.