As it turns out, calculating this is far more difficult than one might think. And then there’s the whole issue of why anyone in the wizarding world would lack cash. Why did the Weasleys struggle financially? Couldn’t they just create more cash? Of course, that raises the specter of runaway inflation and the tragedy of the commons. You’d think they would’ve abandoned hard currency for some sort of magical points system.
I guess we have to assume that there’s some kind of magical non-magic to money in the wizarding world. That is, it cannot be manufactured or otherwise tampered with through magical means.
However, for all their magic, wizards and witches in this universe still seem as thoroughly enmeshed with their economic system as any of us. Their world, like ours, is a realm of rich and poor, celebrity and greed, avarice and repression. Shockingly, slavery still exists in the land of magic. Yet if money is somehow not a part of magic itself, by what mechanism does it infect this world? Money seems to diminish magic as nothing more than a technic. Magic is something practiced, yet wizards remain economic creatures.