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.

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.

In my view, the "native" format that they produced the content in is the format they should be delivering by default (if supported by the viewer's setup). Of course I recognize that people will disagree, after all, UHD Blu-rays also generally cost more than 1080p Blu-rays. But of course, UHD Blu-rays aren't backwards compatible with standard Blu-ray equipment, so it doesn't feel like an artificial limitation simply for the purpose of price discrimination. This also seems to be a no-brainer for Amazon Prime, Apple TV+, and Disney+, which (as far as I can tell) don't have any concept of charging based on video/audio quality.

> This also seems to be a no-brainer for Amazon Prime, Apple TV+, and Disney+, which (as far as I can tell) don't have any concept of charging based on video/audio quality.

Almost every other video service globally does, and of those you mentioned Prime's pricing is mostly based on shipping, Apple TV+ at this point is effectively a PR campaign and not a proper service, and Disney+ is running at a massive loss leader to build share.

Netflix isn't charging a sustainable amount of money as it is. You should probably think of it less as charging more for UHD as offering a crazy discount for lower content quality.