Sure, let's do that. Here's the highest paid employee of all three in 2021 (as that's the last year where there's data on all three):
Internet Archive: $158,777 (https://projects.propublica.org/nonprofits/organizations/943...)
Wikimedia Foundation: $406,339 (https://projects.propublica.org/nonprofits/organizations/200...)
Mozilla Foundation: $337,714 (https://projects.propublica.org/nonprofits/organizations/200...)
I wouldn't classify any of those salaries as exorbitantly large. Hell, I'm fairly certain at least some people shitting on them here earn more than that working at a for-profit.