I'm using a managed hosting plan which allows quite a lot more storage, was thinking of possibly hosting for others in future. I'd mainly just set it up as a search platform though, true.
It depends what you mean by substantial investment I guess!
On managed hosting at least, costs on PeerTube seem about 2-3 times higher compared to Mastodon? It's much higher, but the donations I receive cover the costs of the instances so it's (at the moment) sustainable.