"My opinion is that the only thing really going for the $4000 RCMs is that they are much quieter than anything below them and full automation. Other than that it's just another RCM."
What I am experiencing is a dramatic improvement in resolution, clarity, depth and openness. As others have said, the ability of the stylus to travel lower in the groove because it is now free of gunk seems to be true. The resulting increase in 'vinyl glory' is indisputable. Your 'someday' is here now for users of ultrasonic cleaning! Less surface noise is secondary, but a reality. They are definately not "just another RCM."
As the owner of >3,000 LP'S, the cost per LP is well justified. Even my wife heard and saw that immediately!