A better strategy IMHO is to allow zaps to accumulate, but to overtake the higher zapper, it must be done by a 5000 sat increment block (or pick a fair increment based on product). Think of like a staircase. You have to reach the next stop before it's a valid step forward. BTW, I love the 2nd price auction (DSIC) games. Your solution probably works best for simplicity of implementation.