I just downloaded the entire Classic Chicago Television youtube channel on a whim
a TorrentFreak article got me spooked so I fired up the ol' yt-dlp. Got the entire channel, including comments, description metadata, and thumbnail images.
A significant number of videos were actually unavailable because of an odd YouTube bug where 15+ year old videos were listed as "currently being processed". I may re-run this later (since I ran it in archive file mode) to get the missing videos, as it seems there may be about 300 out of 4911 videos missing.
And that 250GB is probably just the downloaded and HEVC-compressed files. YouTube actually promotes uploading in raw formats for best quality, just 3-4 full-length movies would be enough to fill 250GB for them
And mind you, they have a high number of videos but most are short clips and all of them are low res, 360p or 480p max. Any other channel uploading HD or 4k content will be orders of magnitudes larger for fewer videos.