Assuming each video in its largest bitrate is... 2gb for example, and assuming S3 is $0.025/gb, that's a nickle per month or let's say $0.50/yr for that video.
Next up is reduced bitrates, assume you go from 2gb to 1gb and finally 500mb. Round up and you're at $1/video.
Now duplicate it to AV1 and MP4, and multiply that by English, French, and Spanish (oh, and let's say Japanese and Chinese too for good measure).
So a single 2gb video goes from $1/yr to $10/yr, and you're not doing "the dumb simple thing" for subtitles which would basically 4x your cost over "commodity subtitling services".
Or "simplify, simplify simplify", you reduce costs (cha-ching!), and become compatible for syndication or redistribution (cha-ching!)
... and they would have gotten away with it too if it weren't for those meddling kids!