[hiAndrewQuinn]

Yes! Children love money, and it helps them feel like their efforts have a tangible reward that isn't "increase your chances of getting into Harvard 2% in 10 years". It's incredibly cheap for a working age adult, relatively speaking to the outcomes it can later produce - even $100 per A per semester is a huge motivator for a child who might otherwise reason that they can achieve their goals well enough with a couple of B's here and there. This is definitely what I reasoned when I was younger, and I would have loved a short term counterbalancing reward to give me more reason to push myself.

I also pay my wife, who is currently working through college. At her level the going rate we've negotiated is $250 for an A in her hardest, technical class, with exponential dropoff for lower grades (to simulate how small initial advantages lead to huge compounding effects in the business world). She's gotten the full amount almost every time so far :) but more importantly, she has chosen to put more of her limited pool of effort into those classes and less effort into classes neither of us really care about.