I'd say it's on-topic enough.

Let us discount sci-fi, because scale is a thing, and restrict it to real items in mono-world fantasy/real settings. No Magickium crystals. No priceless artifacts (since The One Ring, from that very setting has more value than that mountain of gold. Hell, even the poorly-defined Arkanstone has more value than the mountain of gold).

King Midas (myth) owns more gold than Sauron, or easily could if he so desired.

King Gilgamesh (Fate) owns more gold than Sauron, for he defines all treasure in the world to be his own and oddly enough no one contests his claim.

But they're kings. They're supposed to be rich (though so are dragons), so let's scale down:

Batman's net worth is approximately twice that of Smaug's. Bruce Wayne may only have 10 billion, but Batman's additional assets such as The Lighthouse more than make up the shortfall.

Either way, that's three characters, all of which would have existed when this article came out a decade ago.