It’s dragon sickness. Seriously. In all of high fantasy, there is exactly one dragon that has more than $1,000,000,000. His name is Smaug. That gigantic pile of good and treasure amounts to somewhere between $10,000,000,000 - $15,000,000,000. In every other story or game, all the dragons (except of maybe one single Red dragon) have less than $1,000,000,000 in gold. (Admittedly the price of gold isn’t helping here)

RAW: all other types of dragons have less wealth than Red Ancient Wyrms. A Red Ancient Wyrm will have between 1,000,000 to 5,000,000 gold pieces worth of wealth. We’ll assume they are a Philistine, and all their wealth is in gold. That means that one single Red Wyrm per world might have somewhere around 500,000 oz of gold. Currently that much gold would be worth just over 2 billion dollars, but again that is the extreme statistical outlier of the literal greediest and most evil type of dragon.