Why are the prizes for the two spots next to the sides always the best ones for pinball machines in night markets? Take a closer look at the paths the marbles roll off. When a marble hits the first separation point, it can bounce off towards the left or right, and then continue to bounce off towards the left o right when it hits the next separation points until the marble eventually reaches the bottom. The image formed by this rolling path is exactly a triangle. This is called the "Yang Hui Triangle" in the East and the "Pascal's Triangle" in the West.
As such, there is a higher probability for a marble to roll towards the middle during the rolling process. There is only one route to reach the left- or right-most bottom spots. That is why the grand prizes are always set at these side spots.