So, for the most part, my guess is that $500,000+ salaries are a form of rent seeking, and are not justified in the so-called marketplace.
It'd be nice if someone could crash together the stats and see if this intuition bears out. You know, look at percentage of donations used to actually help their stated cause, and see if having a super-star CEO actually results in a more well-capitalized charity.
I doubt it, but I depend on evidence, not ideology.