And that is good for you, giving you the benefit of the doubt that you meant 15mbps, but I know I can personally tell the difference between 15mbps and 50mbps. Seeing more detailed film grain and seeing less artifacts in fast moving scenes are two of the most noticeable.
Commercial 4k Blu-ray’s are twice that all the way up to 4x or sometimes more. And I’d say even on the best mastered disks there’s still obvious encoding artifacts.
None. No matter how much you pay, the best you'll ever get from streaming services is a bit-starved encode with fake film grain in a bullshit codec that'll look worse than 720p DVD rips you'd find on Zamunda yet still require more power to decode...