My jellyfin can stream 4K just fine, even remotely through a vpn so i am not sure what you mean.
Depending on transcoding you might require a gpu but still not a standard “gaming spec” pc cant handle.
Come to think of it, my internet provider does allow upload up to 25mb/s and this is the highest end available for consumers in my area. Technically thats a subscription but realistically its bill similar to water/electricity.
The upload limit is also purely and artificial cap, they could easily quadruple it if they wanted.
Also Realistically usecase for 4k movies is usually your home couch so it be streamed on Lan speed. Quality is often better than common stream providers because they do cheat to keep bandwidth down.