I have hosted a PeerTube instance and surprisingly the storage is not a problem because it is very cheap these days.
About the bandwidth, if you enable PeerTube’s p2p tech (WebTorrent) you can have a fair number of users streaming at the same time (but it’s not great for privacy).
I have proposed a network of PeerTube instances to a group of youtubers each with tens to hundreds of thousands subscribers and the benefits/costs ratio looked pretty good to them. It didn’t work for other reasons.
Notice that youtubers earn basically nothing from YouTube except those with millions of subscribers. They are on YouTube just for visibility but if enough creators move at the same time they can also move a good percentage of the userbase in my opinion.