In my experience reading hundreds of IRS 990 forms these number are not out of bounds for non-profits at their scale. Healthcare and university may skew the absolute numbers, but are similar.
Specifically a great executive will personally move the fundraising needle in organizations (+1-5% or more) and mediocre executive can cause losses/missed opportunities in the opposite direction of a similar magnitude. The conventional thinking is the relative fundraising impact of a great vs a good executive may 10x their total compensation, so it's probably worth trying to retain the best.
Anecdotally, I know of a not-for-profit COO who offended an NBA player killing the relationship. His successor COO repaired the relationship, ultimately resulting in multiple millions of new donations and a co-marketing agreement with the team. When the COO was hired there were rumblings because he'd negotiated +$50k over his predecessor.
With no equity and the poor optics of commission compensation or cash-bonuses, big severance packages are one of the few ways an organization can reward employees following years of great service.