it must be doing something right in terms of being sustainable
They’re basically living off of investor money and selling user data. The former is not an indefinite solution though. And Discord Nitro is a fucking joke, the revenue generated from it will never cover the operational costs.
Matrix is a much better solution, it uses peer-to-peer technology (matrix.org/blog/2020/…/introducing-p2p-matrix/) to reduce the burden of operational costs on the team. It’s also federated, just like Lemmy, meaning anyone can host their own Matrix server and communicate with users on other servers. Running Matrix at home or on a VPS is even easier than self-hosting Lemmy. It’s also completely free and open-source and allows everyone to write their own clients. Discord on the other side is a piece of proprietary garbage/spyware and bans everyone who attempts to use a custom client. I will never understand why so many people like Discord.