Those salaries are at or below market for high-level execs in Silicon Valley, especially considering they can't offer stock options. The people capable of managing the large software projects Wikimedia needs can make more at other tech companies.
>>Ekaros+i
Wikimedia is based in Silicon Valley (San Francisco, really), so they're competing with other employers in the region for talent.
The reason they shouldn't move their HQ somewhere cheap is the same reason Apple or Google shouldn't: there isn't the concentration of tech talent there.