The costs to push data are fairly trivial at the moment. Where peertube will struggle due to technical barriers (mostly just storage/duplication), text and images are just not that taxing.

Let me assure you whole it sorts itself there’s no shortage of people throughout the history of new cool things who want to host and play with them. We’re probably headed to maintain those through foundations/donations.

The cool part is just like email you shouldn’t have to be permanently synchronized, meaning you could run an instance you collect like an email client at near 0 cost to anyone.