Even now it costs extra to have file uploads over 50MB, high quality audio, and large video calls. Features that an organisation like this could legitimately need.
we use discord, it's great, we wrote our own bots for the things we need. In terms of making money, it's just discord has a different model for making money, it doesn't want the servers to cost money, it wants as many servers as possible so many people want to use discord. It sells directly to users.
Just takes them to hire the right marketing genius and suddenly you'll be subscribing to send more than 5 messages a week.