Yeah, I'd pitch $25 which includes material, each screen will take a few minutes and you can do it on a weekend. Super easy job. You don't even really need a jig for that small a screen.
Figure out what you want to charge.
My price is based on the fact that most homeowners don't want to remove the dirty screens, load then into their acura, drive across town, drop the screens off, and then a week later go back across town to pick up the screens.
YOU drive out, YOU remove them, YOU haul them in your truck, YOU fix them, and YOU return them and YOU install them.
You put it like that, then $25 is a steal.