P2P video is extremely difficult to do well. Video is sensitive to transfer bitrate, data order, and timing. None of these are things P2P is really good at providing. While P2P can ask for data ordering the actual availability of that order is dependent on the participants in the swarm.
Even then as a host you need to provide seeds for all your videos as a P2P swarm will only ever help with currently popular videos. So in actuality P2P ends up with similar hosting costs to traditional video hosting only providing a bandwidth savings on viral content everyone watches simultaneously.
If I recall correctly, the amount of streams you could support with a cheap VPS + Cloudflare + similar things is pretty impressive.
The reality is most people don't need to be able to handle millions of simultaneous views, and so a basic setup with "p2p on top" might work exceedingly well.
Modern HLS/DASH streaming off a VPS/CDN combination is extremely fast because it's just HTTP as far as the servers are concerned. If you've got a fast HTTP serving system you can serve tons of clients without many problems. Storage however is still an issue. You need enough storage for your content at the distribution edges.
My point is the P2P on top is very difficult to actually build and have work well. Like HTTP serving it doesn't obviate storage needs. You need to seed all of the content you distribute via P2P.
But what's the cost for storage? If nobody is watching your "back catalog" you can serve them off your server (maybe not a VPS, maybe a dedi, but you can get 1 Gb/s and 2 TB of disk for like 130 euro: https://hostslick.com/dedicated.php )
Then you're just down to what the CDN cost is for the "active" video, maybe the last two?
Even then as a host you need to provide seeds for all your videos as a P2P swarm will only ever help with currently popular videos. So in actuality P2P ends up with similar hosting costs to traditional video hosting only providing a bandwidth savings on viral content everyone watches simultaneously.