No, good grades are an expectation. Kids are becoming more and more greedy, this is only pushing it further. Good grades are not something you should only want because of the payment afterwards. Working hard and putting forth your best effort should become habit, something you strive to do. Bribery is not an option that you will have in the real world, there are only consequences. Children should find motivation for doing well in school, but not the kind of motivation that will buy video games and fry their brains even further.