I would imagine the most expensive part is the storage space perhaps Peertube instances can function as cooperatives for content creators where they pool their resources to kickstart their own independent video platform free from censorship and frivolous corporate takedowns.
Oh and if you’re interested in hosting a PeerTube instance then you also might be interested in my channel PeerTube Admin Chronicles: https://tube.jeena.net/c/peertube_admin_chronicles/videos