Technology

150MB per 10min video, and that means it's 390,000Mb (or 380.86TB) for their collection.

Your overall point is fair, but your math here is off by a factor of 1000 - it would be around 380 GB.

It could be done if peertube used a scheme like BitTorrent. We are approaching a time where enough users have sufficient upstream bandwidth for video.

But then, even without hosting costs, creating videos takes much more time and effort than writing a short text.

You are vastly overestimating the amount of storage you need since you are looking at some download which itself has to choose the encoding (which is independent of whatever youtube does: youtube absolutely crushes the quality).
Most estimates assume that youtube has 1 exabyte of storage, let's say we buy this in bulk from retail (which we wouldn't do: you wait as long as possible since storage prices are going down and retail stores would give you the finger if you ordered and exabyte worth).
Let's take that number and run with it:
Buying retail, you can get Seagate Exos X20 20TB drives for 280€, 1 exabyte is 1Mio terabyte, meaning we have 1_000_000/20 * 280 = 14 Mio € (you'd need machines to put those into but you also wouldn't buy the entire thing upfront, and using retail prices either).

Compute also isn't that big of a deal if you do it correctly: the expensive part in video hosting is usually video encoding since to get small video sizes you need to spend compute beforehand to compress it.
However, you can shift this in significant parts to the user by implementing the transcoding in WASM and running this clientside (see e.g. https://www.w3.org/2021/03/media-production-workshop/talks/qiang-fu-video-transcoding.html) in that case users would compress locally in the browser before uploading (this presumably wouldn't even take longer than normal uploads for most people since you trade off transcoding time against upload time).
There are still other compute expenses but those are much more limited.
These mechanisms don't (at least to my knowledge) exist in peertube yet, but would be possible.

The actually expensive part is always the actual networking: Networking is one of the few things that actually get more expensive at scale due to the complexity explosion, rather than cheaper (e.g. having dedicated transcoding hardware drops in price per user since you have higher utilization).
Networking quickly runs into bottlenecks where you have to account for all the covariances between datasets in the network.
Basically to increase the amount of e.g. storage available everything in the network needs to be increased (from the local machines connections, over the cables and switches up to routers and outgoing connections) due to you increasing the density at one point, you have to increase the network everywhere.
That's why networking dwarfs everything: you just get crushed by networking being the bottleneck between your increasingly dense devices.

The clue behind peertube is that this is not as extreme of an effect due to

1. federation (certain connections just aren't dense due to the overall network topology being distributed)
2. torrents

The latter is the important part: instead of having network cost rising (super) linearly to the amount of users you have it rise linearly to the amount of simultaneous unique videos.
This is a much smaller number which means you do not need to compete in that space, which is the dominant cost factor. (if you have a method where one user can retain the video and share it without actively watching that same video, you can probably get real-world sublinear scaling)

Mind you, the costs involved here are still large, but not insurmountably large, especially considering there is not one unique organisation that would have to pay for the entire thing and its not an upfront expense. Fundamentally though the system is built such that it won't be crushed as users flood into the network.

to be ran

to be run

You don't need a centralized platform to have recommendations.

You just let users choose some tags and go from there. Each server will surface different videos, but if they all pull from everyone they're federated with it would be a lot more accessible pretty quickly. And let users opt in/out of watch history tracking to feed their suggestions.

It won't have the potential YouTube does, but YouTube's so compromised on intent that it could easily be better in practice if content availability were the same (which is obviously way off).

If you have a bunch of people guess how many M&M's are in a jar you can average the guesses and you'll come very close to the correct amount. A recommendation system can be very democratic in that way. When reddit still had their public API I would take advantage of this fact and use it to decide if something was a "deal" or not on PC parts. I was tracking the prices of computer ram at the time as an experiment. It worked very well. If they are federated properly, then their content can be filtered and appear on an instances front page.

That would be like saying Patreon is monetizing video.

No. I mean ad-supported income that automatically comes with YouTube. Not to mention members subscription and Superchats which are also built in functions and represent significant part of content creators' income.

And I don't think we can solve this easily. I've heard bigger creators say they want to make money with their videos. And Peertube doesn't do ads, so it doesn't pay the creators. And we're kind of going in circles now anyways because your initial suggestion was to switch to Peertube because of the YouTube ads. We can not have them and don't have them at the same time.

Maybe the solution is sponsoring. I heard ad revenue had declined anyways and many creators mainly rely on sponsoring nowadays.

Bold of you to assume they would stop rolling ads instead of simply requiring a "fair and reasonable ad supported tier".

A lot of people have jobs doing creative work like YouTube, even before the age of YouTube people where creating stuff such as TV Shows, Radio and Movies (Legacy Media). Sure a lot of people would still create something in free time but the reason people create quality content on places like YouTube is because they are being paid as a bonus, otherwise they wouldn't be able to spend as much time on the content they create.