I've never been paid for good grades. It was expected that we get good grades (until my little brother hit school all A's were expected). It wouldn't have been remotely fair to pay for grades - my sister had all A's because she worked her butt off, I had mostly A's because I'm a pro at operating under the radar, and my brother had terrible grades because he hated school. My parents tried a ton of stuff to motivate him - money, they offered to buy him a gun, they threatened to keep him from wrestling, etc. Nothing worked. Looking back on it, I think if someone had sat down with him every single night and gone over his homework with him, he would have done so much better. Just like if someone had bribed me with one-on-one time with either parent I would have been more motivated.
Until my sister and I moved out my parents didn't really have money to bribe/pay us with anyway. It was expected that we do chores, help around the house, get good grades, do sports (if we wanted to), and get a job to pay for our own stuff because that's what you do in a family. My sister and I both started working around 13 and worked all the way through high school. I really hope that I'll do it different with my kids - I don't think there's anything inherently wrong with my parents' tactics but they relied pretty heavily on emotional manipulation to get what they wanted. It was unintentional but it's left some pretty lasting marks on the way we all behave.