It all began with the free-to-play titles: a game that is theoretically free to play, but that involves in-game purchases to either enhance the experience or to get past a certain level. The model existed on PC, but was never a major player. It wasn't until mobile gaming that we saw a rather constant implementation of free-to-play. Nearly ever successful mobile game, from Candy Crush to Pokémon GO has implemented the free-to-play concept well.
At some point, however, the model of in-game purchases left the semi-exclusivity of free-to-play and migrated to paid games. There had always been DLC for games, but playing a paid game without the DLC was never painful or impossible; only adding bonus content to an already established game. Today, that isn't quite how it works. Often times, when you purchase a $60 videogame, you only get part of the game. To play the full game, you still need to purchase additional content via in-game purchases.
The most controversial version of this has been Star Wars: Battlefront II, a game that would cost over $2,000 worth of in-game purchases to get the entire game. This game prompted a Congressional investigation into in-game purchases and loot boxes in games, which is still ongoing. However, the ESRB, the US videogame ratings board, has decided to take at least some action on their own.
Starting soon, the ESRB will be creating a campaign to inform buyers of physical games, either in retail or from online, that a game contains in-game purchases. In addition to the ESRB rating, retail packages will begin featuring a warning, similar to what we see in mobile app stores, that a game has additional costs.
The new In-Game Purchases label will be applied to games with in-game offers to purchase digital goods or premiums with real world currency, including but not limited to bonus levels, skins, surprise items (such as item packs, loot boxes, mystery awards), music, virtual coins and other forms of in-game currency, subscriptions, season passes and upgrades (e.g., to disable ads).
There is no announced launch date for the new labeling, but the ESRB does promise that it will begin appearing in the "near future."