"In my company that I was working for Diablo IV Gold, we had weekly events that offered unique prizes They were also designed in a way that you could [...] win it using uncommon in-game currency, which could allow you to win one of the major prizes. The designers also had to offer additional milestone prizes in addition to the first prize, and that would usually require spending real cash to get ahead in the event. A lot of our milestones and measures to determine whether an event was successful is the amount folks spent. We did take into account sentiment, however I'm sure the upper-levels always wanted to know if that event helped people spend."
Real-money transactions aren't novel by any stretch or imagination. Diablo Immortal didn't pioneer them and it's insincere to make that claim as truth. This action-RPG by Blizzard isn't really the primary of the problem, but instead is the most savage amalgamation of free-to-play mobile as well as PC games. There are two Battle Passes, each with different rewards, each only available to characters (and not included in your general roster) and with too many different currencies that it is difficult for an average player to keep track of, Diablo Immortal's economy reads like a huge mobile marketplace.
Although they are sometimes opposed however, have become commonplace within the overall industry. One could argue that use of loot boxes and other real-money transactions in AAA games has created this type of economic predatory business, but the more that AAA gaming moves towards the model of games-as-a-service as it shifts to the games-as-service model, the more in common with the mobile gaming that has existed in this highly popular area for nearly a decade.
And this isn't just reflected in the use of currency paid for items however, it is also evident in gacha mechanics, and the publication of drop rates of the more scarce items. Gacha is the act of using in-game currency, whether it was free or purchased via an in-game store, in order to get something you want or pieces of equipment for instance, in the case of Dissidia Final Fantasy Opera Omnia buy Diablo 4 Gold, or characters in the ever popular (and long-running) Fate/Grand Order or Genshin Impact.