How so? e.g. anywhere I've looked, schools are a huge part of the budget. Special education alone is over 10% of the county budget where I live. Schools in total are over half of city+county. The elderly wouldn't be contributing to service demand there. They're likely also not going on tons of crime sprees necessitating police, generally another large budget item.

Like another poster said, things like pensions and medicare might overall drain the entire economy, so the end result is the same, but that seems more diffuse than local tax bases, and wouldn't properly appear in local government budgets.