to buy or not to buy (ultrasonic record cleaner)

My best friend has one. He is very pleased with it.

@lukaske has what? A Monks machine? An US machine? Which one?

"doesn't clean down to the 2-5 microns in the bottom of the groves"
An elliptical stylus is 0.2mm to 0.7mm. 2-5 microns is 0.002-0.005mm.
The stylus does not go anywhere near this. 
https://www.vinylengine.com/turntable_forum/gallery/image/22429
And, the oily natural surface of an LP is needed to lubricate the groves.
It is necessary to keep some oil in the groves. The KM fluid is highly refined to leave the "right" amount of oil.
A major benefit of the KM RCM it that it cleans near 100% of the excess dirt. Whereas the ultrasonic method circulates all the dirt in the fluid. And then blow dries the residual on the record. Most don't change the fluid very often. And how it takes 5-10 minutes instead of 1 1/2 minutes of the KM.

I didn’t like the sonic signature of the Monks fluid. I use a Hannl fluid which is no longer made and will eventually have to find another fluid. I also use AIVS #15 for a deeper clean, agitating with a unidirectional pad applicator that came with Lloyd Walker’s Prelude kit (you can buy replacement pads, but unfortunately, not the applicator, separately). I do use the Monks brushes for the Hannl fluid and for the rinse stage. I think the rinse is critical.
After pre-cleaning, I use the KL ultrasonic and if I’m really concerned about the results, will dry via the Monks using a little more high grade water.
I think the combination of methods- essentially manual cleaning, combined with vacuum, and ultrasonic, with appropriate rinse steps, is synergistic. I’m agnostic as to product brands-- I’m looking for results. I’ve gone through a lot of records and have a pretty good regimen that I’m satisfied with, but am always open to learning.
I’m also not about ritual or voodoo-- if you can get a record clean, and remove the contaminants including those bound up with the cleaning fluid so you are not leaving a residue on the record, you should be good-- even without spending a lot of money on fancy equipment. The equipment is a convenience. I like the Monks and it is one machine I’ll keep. I like the KL too for that matter, but most ultrasonics eventually die or need parts that aren’t readily obtainable. DIY ultrasonic makes a lot of sense. For those folks that don’t want the trouble, the Degritter is apparently the current fav and I’ve heard almost uniformly positive comments about it. As mentioned, I’ll go industrial when the KL finally dies (not that I’m wishing for that, it has served me well).

Hi all, 
Robert here, 
I started a similar thread on AK, especially since I'm seeing the machines on Ebay starting to hit the sub $300 mark. 

Here is the one thing no one else has brought up. 

Your dedicated record cleaner/vacuum system is just that. An Ultrasonic cleaner might be an easier thing to rationalize purchasing because it can be used to clean other things, eyeglasses, jewelry, dentures, alfa romeo parts, etc. 

It isn't a one trick pony.