They are common as heck. They just never get reported. And NRA own demographics tend to be in rural states where these salary, remuneration or spending numbers seem large, when they are not.
About seven years ago a major non profit membership association client of mine got embezzled for $4.1 million by its executive director and accountant. It was a huge loss since their annual operating budget was about $700,000 million, about half paid for with member dues and about half from their endowment. Worse yet their insurance maxed at one million dollars. The sole and entire public/media coverage was a single three sentence piece in the trade publication for not for profit news. Nothing in the WPost, NYTimes, WSJ., etc.
Let's keep in mind there never would be a real examination of Everyone, "March For Our Lives, "Moms Demand" books and a public and publicized investigative pieces. Those are pure top down, narrowly controlled groups that are media darlings.
As far as NRA sending more than taking in, virtually ALL non profits do that in some years or sets of years. In the case of the NRA, Kendeda and several of the gun control groups specifically -- and successfully -- targeted a good deal of NRA's funding.
The NRA did significantly expand its costs in administrative overhead last year even though it froze their pension program, reduced lobbying budget and cut spending on education and training by 25%. If it reverses, okay. However with the rumors (claims?) of extravagant spending by a select group of directors and WLP, it is troubling at a minimum.