the reason why an atproto relay is so large in storage is because to validate (this is the authorized transfer part of the name AT Protocol) a record it has to know about all previous records by that account, so in effect it had to store the entire network on a relay, which is how you get these massive sizes.
that's what bsky is currently fixing, see this thread for more details https://bsky.app/profile/divy.zone/post/3liwwg45izs2r
there is impact on offering hosting services for a PDS (which no other company is seriously doing right now), that part does get more expensive if you offer larger video storage. Bluesky PBC can eat that cost with VC money, but more difficult as a startup
it also does directly affect costs for running a CDN. So an app like Skylight, which is a bluesky video client that has a tiktok-like interface, if they want to get more independent from bluesky pbc they'll have to use their own CDN at some point, since currently theyre fully dependent on Bluesky's CDN. If they would do that, the upgrade from 1min to 3min video does affect cost
(then again, for Skylight, bsky's focus on video is likely a net benefit anyway, ¯\_(ツ)_/¯ )
