It seems like GTA Online has practically been feeding Rockstar and Take-Two Interactive on its own in the past few years. The multiplayer portion of the latest installment in Rockstar's legendary and renowned Grand Theft Auto franchise has increased the mainstream popularity of the game hundredfold and opened up a whole new source for revenue via in-game microtransactions.
GTA Online has broken numerous records in the past. It is among the most players non-free-to-play multiplayer games with over 8 million unique log-ins every week. The game has passed the 65 million shipped copies mark a good long time ago, and that did not account for digital sales.
However, the most impressive record that it achieved was the revenue generated by its microtransactions. Shark Cards, as they are called, can be bought by GTA Online players for real money, which grants them in-game currency. There are various tiers of Shark Cards. Naturally, the more expensive the card, the more in-game cash it gets you, with the largest one being the Megalodon which provides 8 million for $100.

Now, in GTA Online the high-end things have always been priced at a premium, truly making them luxury items and indicators of wealth. Accumulating cash in the game through traditional methods takes quite a bit of time, though it's not difficult by any means if you know the right techniques.
Nonetheless, with Rockstar constantly updating GTA Online with new content updates containing tons of interesting new items, vehicles and properties, all with a large price tag, players have been gobbling up Shark Cards with a fervor.