On top of that, assuming they will have zero effective cost increases is wrong. There is so much growth left in content and users. How much has Wikipedia grown in the last five years? How well do they cover non English languages? What if they had the same size article base in English as every other language? What if every internet connected user could use Wikipedia?

Saying we could freeze Wikipedia costs in 2019 based on $90M in the bank is shortsighted.

The page on The Wikimedia Endowment is actually quite interesting if you're into finance and investing - https://meta.wikimedia.org/wiki/Wikimedia_Endowment.