3. World of Warcraft - The Value of Money
World of Warcraft, like the best MMO games, is based on a real-world economy, whereby there is a limited amount of cash circulating (at least in theory), and players have to keep track of what they're spending and making in order to keep progressing through the game. One of the main things is to ensure that you grind enemies and farm their gold, in order that you can save up money for the best gear and weapons, such that you can then get through the more challenging quests and reach the end-game. There's nothing worse in a game like this when you want to buy some new armour or a new sword, but it costs an absurd amount of gold, and you need to spend the next few hours grinding just in order to get this weapon, and then proceed through the quest. It slows the gameplay down, a form of punishment in a sense for not budgeting better; keep your eyes well-trained on your gold reserve, because when a taxing quest rears its head, you just might need to splash out unexpectedly, just as you would if, say, your fridge or boiler suddenly broke down in real life.