Presumably those fans are buying those things at least in part because they want to have the album, concert experience, or merch. With twitch donations/tips yo

Presumably those fans are buying those things at least in part because they want to have the album, concert experience, or merch. With twitch donations/tips you get comparatively very little in return - your username might pop up in a video overlay for a few seconds, and the streamer might be like "hey thanks, [username]!". Those 3-4 seconds are typically the entirety of your several-hundered-dollar experience.