My son has been doing worksheets for the final 7th grade math test, and, almost as a joke, we offered him fifty cents for each problem he finished. He immediately finished 36 problems in about ten minutes. We don’t do “dollars for A’s” or any other sort of direct rewards for grades, so this was a new experience for him.
Of course we teased him that he’d really spent two hours whining about it and ten minutes working, and he fully realized that he was doing it for the money.
A bit later, at bedtime, it hit him, “You guys do math at work and get paid!”
I explained that a lot of the math I do was far more boring than reducing quadratic equations to standard form. My “math” tends to be adding up the search page result clicks from varying sources, divide by the total search attempts, express as a percentage, and repeat for the next day. Whee!