I'd suggest that the law of diminishing returns almost always applies but that the breakpoints are highly individual and driven based on how much value is placed on audio (preferences) and resources. If you don't value audio, then spending $2k on a system may be a waste relative to your bluetooth speaker. If you really value audio but have have limited resources, then perhaps you can justify buying a $3k integrated but not $8k in separates. If you are Jeff Bezos and you value audio, no big deal to buy a $90k PC (but you may pass on that audio barrier breaking new $1 billion amp as you'd get more personal utility value out of a another yacht).
The law of diminshing returns?
Came across this article today, just wanted to share it for your perspectives. https://hometheaterhifi.com/blogs/expensive-dacs-what-exactly-are-you-getting-for-the-money/