In my state, you pay the usual annual license fee, plus an additional annual fee for the cause that the person is supporting.
It doesn’t cost that much, in my opinion.
The donation/charitable part is tax deductible, if a person itemizes on their taxes.
If you’re getting special plates for the first time, there is a small additional fee, plus the other costs. Then after that, you just pay the annual fee plus the yearly contribution part of the cost.
The exception to these costs might be hobby or collector plates where the fees might be higher for something like that. Someone would have to check with their DMV office on that, to be sure of the fees on those types of plates.