The $200,000 average salary for each employee is plain wrong.
In that form, there is a section (Section VII) for the highest paid employees and requires WMF to report any employee who was paid more than "$100,000 from the organization and any related organizations". And only 11 people in all of WMF were paid more than $200,000 in that FY and the highest paid employee took a little less than $400,000, and in total with the rest it was only 12 were paid more than $100,000 (at least according to the form).
There are lots of complicating factors, including the fact that most WMF
"employees" live outside of the US and thus are hired through the
Employer of Record (EoR) system. So they show up as contractors in the
list of staff and I'm not sure where their expenses show up in Form 990.
Staff compensation gets adjusted to where they live and usually
(virtually all but not sure) it's less than salaries paid in the bay
area due to the fact that simply living in SF (and bay area) is expensive.
If you combine total expenses of WMF with personnel expenses (~80M) and divide that to 400 (~ number of staff in 2019), you might get $200,000 per person but that includes data center expenses, buying hardware expenses, network expenses, money paid for renting offices, electricity bills of the dcs and offices, travel expenses, basically anything you can imagine except grants.
(In my volunteer capacity, It's weekend)