There's a mistake I see in the comments here that "non-profit" = "charity". There are a large collection of non/not for-profits that are not even remotely in the charity business. Some of these companies have long legacies that stretch back to academic labs spun out of major U.S. educational institutions.
I've worked for two such companies in my career (and partnered with a few others) and both of them were really just normal businesses that used their non-profit status as part of their business model. They used that status to position themselves as an objective second party to various governments and businesses and signal trust. They also internally represent themselves as something different from commercial businesses, just with a weird way of mopping up profit at the end of the fiscal year. At one I was a researcher and the other a low-level executive.
At the working level, both paid slightly under comparable jobs in the private sector, were often very top heavy, and spent lavishly on facilities and had large internal R&D programs that often went nowhere but acted like overamped hands-on training programs that expressed themselves in additional expertise they could offer their clients without having to turnover staff.
I often had multiple personal offices, subsidized mid-level restaurant quality lunches, laboratories, assistants, and research budgets stretching into the low millions of dollars. This was in addition to the regular work we were contracted out to do, which was often either direct work on fairly cutting-edge S&T like programs or providing special advisory and expertise services to those same customers.
All of the companies I know in this space are also fairly top-heavy with, executive and administrative pay helps sop up any profit.
The law requires these companies to report quite a bit of information about their financials into the public space every year [1]. Some of the executives make quite extraordinary pay.
https://projects.propublica.org/nonprofits/