I would say it's a dangerous road. Child or not! Imagine being challenged at work... in a sales team, for example. Make a sale, get to do a lucky dip. Say two

I would say it's a dangerous road. Child or not! Imagine being challenged at work... in a sales team, for example. Make a sale, get to do a lucky dip. Say two people make an equivalent sale, one wins and the other doesn't. I would personally feel less motivated if I lost. I wonder if you did it to kids, they would learn to weigh up whether doing any given task was worth some arbitrarily set lost/win. It's the difference between learning that "washing a car is worth $10 of my time because it will takes x hours and the cost of soap is y and so on" vs "washing a car is 50/50 worth nothing or $10".