If your buying knock offs and painting and selling those take what your actually making off the bait and charge that for just the paint job. If they are providing the bait, some painters charge more if the hooks and split rings aren't removed or if the bait needs extra prep work ,say an old used plug with chips or scratches.there are Alot of variables, some charge more according to the length.some patterns definitely take Alot more time than others, so really it comes down to what you feel comfortable charging people.also you might try to check out other custom painters Websites see if they provide pricing maybe this will give you an idea what thw average painters charges,like you said you don't want to overcharge people but you also want to make it worth your time.