[Qwertystop]

Storage and production costs for something available in UHD are the same regardless of whether someone streams a downscaled version. Storing multiple resolutions (assuming they do that rather than downscaling live from the stored highest-res or making the client do it) is where additional costs for more versions would show up.

[pilsetnieks]

You need to store downscaled versions anyway for low-bandwidth clients. However, with UHD you also have to store the UHD version, in addition to all the small ones. You also need more storage not just in your own DCs but also in those cache boxes you have at every major ISP; then there's the peering costs for transmitting those UHD videos, etc.