I put together a top notch ear monitor setup using existing iphone and Roon streaming software for <$200.
Cost goes up from there for other applications depending mainly on room size and other more subjective considerations. Multiple source devices will also up the cost accordingly.
I have <$3k invested in my family room system which I suspect is one that most people might be able to live with.
I’ve managed to bring down the cost of my "reference" system by several K in recent years but still way more than any of these.