rather more of them than on earth, according to the article.
Wowhead, the database of Warcraft items, lists 1,203 types of currency in the game. To be fair, some of those have been retired, and others are currency for a single item or purpose—but in comparison, the entire world (not of Warcraft) only has 180.
It appears that there are 180 currencies recognised by the UN. It also appears that there are less independent currencies, the example I saw was the Danish Kroner which has a fixed exchange rate with the Euro.
What I don't see in this are other forms of exchange. There's the obvious crypto currencies, of which I'm in no doubt there are plenty.
But that's not the only way to exchange value. Barter is one, donation is another. I suspect that there are plenty more.