Well now you can know. Guidestar lets you pull financial data on all sorts of non-profits (charities, schools, ministries, you name it). For free (mostly–some reports require a modest fee to access). You can quickly see each organization’s revenue vs. expenses for a recent year. The 990 Forms are particularly instructive–you’re basically looking at their tax forms (where they get their revenue, how they spend it, and more). Buried in the 990 forms is data that can be useful if you work for a nonprofit, or are seeking to do so, and want to have a sense of what the salary expectations might be at a particular level (director, vice president, etc.). Top salaries vary widely depending on the organization’s size and scope, but these data can be found in Part VII of the 990 Forms.
I hope Guidestar helps you give generously and with discernment to causes that you care about.