The point of my post was to highlight the fact that poll taxes weren't struck down on the rationale that taxing a right is per se unconcstitutional.
Poll Taxes in federal elections ended by the 24th Amendment.
In local and state elections I believe they were struck down on equal protection grounds. (Not sure, and don't have time to research it right now.)
If the fee/tax isn't designed to prohibit/discourage the exercise of the right then it's a tough row to hoe.