Along with the premium version, they have a crypto currency (TON) that can be used to buy things on the platform from other users, and I think you can also buy things with real money and they keep a small commission. Also there are some small ads in very large channels (not groups, channels only) and ways to gift “stars” to other people, like Patreon or sth
Paywalling a better resolution than the ones ALREADY present on the platform, may be the best way to approach the issue of it being fucking expensive to serve it.
Youtube has gone to shit and the enhanced 1080p bitrate is not one of the reasons