Would love to see any numbers that are involved in working this out, how those numbers are trending, and if it looks like they will arrive at useful values any time soon.
Keep in mind it started out viable.
Broadband did exist even when most people were still on dial-up, and with every major ISP their generic plan included your own personal web space from which they would serve your content to the world.
All you had to do was upload your content to your own web address, and throw in some html or PHP if you wanted to.
Even if all you had was dial-up, you could (slowly) upload a decent length video, and after that anybody with broadband could watch it with full FPS.
The original webcams were jerky and blurry by today's standards but they live-streamed just fine using Windows XP and the free Windows Media Encoder. Anybody using Windows Media Player could view the stream directly without need for a browser. Also players like VLC work for Linux or Mac users.
Now OBS is a common app for streaming (broadcasting) today which allows you to encode or compress the video (output) or stream however you like. An HD webcam, fast PC, and fiber ISP connection can handle a number of simultaneous viewers at full FPS.
If you mean "without a CDN", then as someone whose daily job is delivering millions of users high quality videos, I would ask: why would anyone do that? It's like saying "I'll dig my own fibre to the home..." Sure, you may do it if you have no choice, or you simply use an ISP.
CDNs distribute the load and make it more economic to deliver your content. They provide lower cost and better quality streams through more servers and higher available bandwidth.
Sure, you host the videos, you act as the origin, but the CDN sits in front and takes the load. You only have to worry about cache efficiency for your bandwidth. But I can say that you can serve millions of users with 10Gbps and a good CDN, which is feasible for home internet in some places.
For the self-hosting numbers, without a CDN, just take the average bitrate and times that by the number of concurrent users. So you are going to be looking at 6Mbps * 100 users = 600Mbps upload, plus about 10-20% overhead/margin.
To be more explicit: you can probably host video now at lower definitions. The question is how low you can tolerate.
If you've got enough usage where bandwidth starts costing money, go get a cheap hosting with 'unmetered' bandwidth, and maybe that can get you through until you have enough bandwidth usage to get decent pricing.
You should define "complete control". Do CDNs count or not? Why?
Someone recently sponsored dev (putting it on the roadmap) of remote transcode runners to enable better horizontal scaling if that’s a component of your use case.
If you’re maxing out a dedicated server, should probably consider a CDN.
Traffic is cheap you get 100mbit and more for this. 100-1000mbit/your avg Bitrate = streams in parallel.
The hardware side is a no-brainer. Just doesn't matter just sending bytes is easy.
You could always pay Vimeo to host your content.
How about putting the file on IPFS and making it available to the world? Or use GunDB to stream the content.