I'm not entirely convinced that this is entirely some sort of widespread bad behavior. Many non-profit boards conduct research on salaries and essentially size their organization and pay something akin to a market rate for the given size and scope.
However, even a small percentage of bad actors finding a way to inflate their salaries will, as a side effect, inflate salaries across the board because it influences the process that sets the salaries for the honest organizations.
It's a fun problem.
