This was tried on Diablo 3 and found game breaking for a couple reasons. I’ll not go into those details here. There is a YouTube video about it.
Auction House where you can buy and sell gear for in game currency and/or real world funds. You read that right. You could sell your legendary sword of whatever for ■■■ amount of in game gold coin OR $$$ in real currency. Linked to PayPal or a credit card. One of the things that hurt that game was a short lived duplication glitch that allowed ALOT of gold to be duplicated and used to “buy” high end gear that was resold for RW $$$. Quite a few people made real life bank.
Some of the issues that would have to be addressed would be a way to bank in game currency safely. Maybe have two versions. One that you can pickup or loot like currently and is usable only on that one server. And one that is linked to your gamer profile that goes with you server to server and isn’t lootable. Both are used for server specific transactions but with different rates of exchange. An example would buying a legendary sword. It may cost you 10k gold coin of the first type or fifty digital of the second. Selling it would be the same. If RW currency is used, it may cost five USD. Or which ever standard for the region of the server.
The digital version should only be earnable in transactions not farmable/lootable in game. It can be kept in this form until the gamer decides to “cash out”, then it would be exchanged for RW currency and credited to a card on record or sent to PayPal.
The devs could charge an “Auction House Commission” every time someone cashes out. This could be a small or large percentage. Personally I wouldn’t gripe if the commission was half. Because that is half of something I earned for free while playing a game. This commission would also keep people from cashing out too often. Most would wait till their bank was stacked, all the while, the devs are collecting interest on it.
There are several games out there that prove people will spend real world money on it. Even free to play games like FortNite, and the mobile game Game of War. FortNite, you’re buying nothing but cosmetics. Be it skins, emotes, or even dances. Game of War is more along the lines of pay-to-win.
Now I know there are things I’m missing. This is just a concept idea. It’s not even an original idea. I’m sure others have thought the same thing. Probably even in these very forums.
Just my two cents.