There's also subscriptions. People will pay $5 to subscribe to a channel for a month, half of which goes to Twitch (other half to the streamer).

In addition to just subscribing to 1 channel, people can also subscribe to "Twitch Turbo," with gives all the money to Twitch.

Top twitch streamers can pull 6 figures a year. I don't know what the bototm line for twitch looks like though.

Advertising and partnering with big gaming contests can generate real revenue.

game publishers also have paid twitch for front-page visibility during release hype.

I have a feeling they pay quite a bit.

Not really. The networking costs to stream to that many users is huge. Google has the infrastructure to change the cost structure but it only works with that kind of scale.

Ads, subscriptions and merchandise all come to mind.