1 Lambert: {to the blacksmith} 2000 gold pieces?!
2 Lambert: You do realise gold is incredibly scarce and medieval societies mostly used debased copper coinage?
3 Lambert: Even the existence of monster-guarded treasure caches plundered by heroes and redistributed can't sustain such rampant hyperinflation!
4 Smith: So you're skint, then?
4 Lambert: Yeah.

Most medieval fantasy roleplaying worlds seem to have a lot more gold floating around than our world. Everyone's buying stuff with hundreds or thousands of gold coins!

And if you make the assumption that those are heavily inflated prices caused by adventurers running around looting evil temples and dungeons and spending thousands of gold pieces in the nearest towns, you end up with merchants being astoundingly rich and everyone else unable to afford anything. This leads to a situation similar to Spain in the early 16th century, when American gold and silver started flooding into the country, stirring up sweeping social upheavals and setting the stages for riots and revolutions.

Basically, your average medieval fantasy RPG world economy and society should be in a right mess.