I think it's just the dissonance of trying to shoehorn capitalist economics into a feudal setting. In most feudal societies, the money economy, in the sense of everything having a monetary value and having few barriers to exchange that commodity for money and vice versa, isn't fully formed but coexist among different forms of exchange like barter and feudal obligations. The money economy mostly exists within the context of merchants and traders.

Some peasant finding a valuable ring doesn't mean much if they live in a feudal society where peasants can't own personal property, meaning anything they touch automatically belongs to their feudal landlord. The peasant can't quickly pawn off the ring since most merchants with that amount of coin aren't wasting time in some shitty hamlet. And if the peasant somehow flees to a medieval city in order to find a merchant to sell the ring, well many medieval cities require papers in order to actually enter in the city as a precaution towards fleeing serfs among other things, so the peasant would have to either bribe the guard somehow or sneak their way in. And once in, the merchant would almost certainly offer a price much lower than what the ring's worth since the peasant is in a completely precarious position by virtue of being a refugee.

In a weird way, the high fantasy imagery of some adventurer standing triumphantly over a huge pile of gold coin is just another example of capitalist realism. Gold coin is just a placeholder for money, and we associate money with wealth and power because in a capitalist society with a fully formed money economy, money is wealth and power. But this is not so in a feudal society, where the source of wealth and power is not money but land. The way to make it big in a feudal society is to be created a hereditary title through faithful service to your liege. That or be a warlord who's able to integrate to polite feudal society through a strategic loveless marriage.