In computer games players control characters and earn money by doing quests and killing monsters. They spend these money for upgrades and other neat stuff (such as own house, animal and etc.). But this mechanic has inherent problem - earned money are created literally from nothing. The money, which goblin chieftain had, were never used in games economy. They are just a reward for player. The same, though less obviously, story is with NPC - they give the same task they were programmed to give and the reward is also preset. Game economics has nothing to do with reward given. If player is just one, then there is no problem, but if you, as a game designer, have thousands of players... you will soon have to face a problem of hyperinflation. More on what it is and how game designers combat it in the following Extra Credits video.