Now re-contextualize that as if it were an employer/employee relationship. That's actually a pretty messed up lesson to teach a kid about negotiation and self worth.
It teaches you that you should _also_ consider your own long term goals, as opposed to only chasing the someone else's short term goals. I think it's a great lesson to teach a kid about self-worth.
This seems like someone else imposing their own long term goals onto you because they allegedly know better.
You didn't describe any explanation of why good grades are an important step towards your own long term goals.
I'm not saying that paying for grades is a good way to motivate kids. I'm saying that framing it as "I won't pay you because it'll make you lazy" is a very weird way to teach a kid about long term payoffs.
