Past performance is a terrible predictor of future performance. Ssd prices dropped a lot since the pandemic since demand dropped and the factories are still there. As usual this normally means that new factories will be delayed and prices will be relatively higher going forward for a while. Now the longterm trend still favors ssd but 2022 Is a shitty year to base your price projections on
Well USB can only power a small mostly 2.5inch external drive and cannot really spin most large 3.5 inch drives.
And once you want larger sizes or more reliable enterprise drives which are in most large external usb drives you need power. If you are happy with a smaller ( and most likely less reliable ) 2.5 inch drive usb only is of course more convenient.
50000 users at 20gb is 400kbit per second per second? That ain't gonna cut it even for potato quality. The recommended bit rate for 480p is 5 times higher the recommended bit rate for 720 ten times higher. So you maxing out at 5k users makes sense.
Now I am astonished a single server can service 5000 streams at rge same time. That's some scalable server software.
A 10tb+ shucked ( buy an usb enclosure and break it open) drive is a good low coat approach with some risk
- wd only makes nas or enterprise drives of that size so you are very likely to get a high quality drive inside a large WD usb enclosure. wd doesn't make special drives for these enclosures they use what they have lying around
So they are often great value for money with some caveats
- while all the 14tb elements I shucked where Hitachi enterprise drives ( most reliable ones wd has ) they reduced speed from 7200 to 5400 rpm
- they often use a newer sata standard connector that may not work with older motherboards apparently in that case you can tape of one of the pins
- depending on your country you lose warranty. Although in the US you seem to keep it
I have 3:2:1 for my crucial data ( pictures of family and travels and digital documents like tax returns). Basically one main copy another copy on an old nas with shucked drives not connected to the internet and one cloud copy. It is worth it because I would hate hate to lose that data.
I have 2:1 for my media. Just a local copy . If the apartment goes up in flames or a freak lightning burns it down I will have to re-download it again or I will live without it and ghats fine. For a long time the media had no backup but just raid and snapshots to protect against hard-drive failures and dumb user errors.
It's all about your means and risk appetite.