At least when I look, YT premium says it is $140/year (or $276/year for a family plan), and Netflix is $216/year. Spotify is $144/year. It's certainly possible to find drives at ~$10/TB. Call it $15/TB if you don't get a great deal and if you want to add some parity.
The more interesting point though is that at ~5 GB/hour (a decent bitrate, especially for youtube) and $15/TB, you're looking at ~$0.075/hour of video. If something isn't worth $0.08 to keep, is it worth your time to watch? This is probably a question media companies would prefer you not ask yourself.
I don't think your entire family will be streaming 4k at the same time on a Comcast budget connection, as the NOC would start capping your bandwidth rather quickly.
Something about media compression that drew our attention to quality versus efficiency:
"Typically, the production style of low quality media of the same duration creates smaller compressed video data." (Joel's corollary 6)
This was mostly because the producers increased the number of re-used video clips like stock-footage/B-roll, lower grade non-broadcast quality audio, and filming style focused on simpler tripod work with low-textured similar looking environments at fewer locations. Thus, the self-similar nature of low budget films made relatively smaller files, and were compressed into shorter track lengths on storage media.
While the budget constraints are very indicative of bad film, it does not necessarily always mean relatively smaller video files for the same media playtime indicate lame content. However, of the thousands of titles we processed at that company, it was correlated most of the time if all other factors were held the same. Now some people did like "The Chronicles of Riddick: Pitch Black", but with perceptual compression it was a tiny track-length compared to most other films.
I'd wager streaming media ultimately has similar unconscious fiscal incentives to create lower quality content that decreases distribution costs.
The more interesting point though is that at ~5 GB/hour (a decent bitrate, especially for youtube) and $15/TB, you're looking at ~$0.075/hour of video. If something isn't worth $0.08 to keep, is it worth your time to watch? This is probably a question media companies would prefer you not ask yourself.