A method used by game developers, especially in hyper casual
mobile games, where a game will be free to download, however users gain an unfair advantage by paying for in-game currency which normally is relatively hard to get. Sometimes games implement an in-game currency that's only obtainable by paying, whose only use is to be converted to a different currency which can then be used to buy items in the game. This is a very common trick where developers abstract money into in-game currencies so players are
distanced from the consequences of buying it.
These tricks are most commonly used in games by companies instead of
indie games since they rely on making money and for the most part don't care about the quality of their games.
While this trick being very known and frowned upon by the gaming community, developers still manage to trick enough people into paying in their games to keep their business going.