What are the most balanced relatively neutral cartridges at each price level ?

Oh, I forgot to mention the element of subjectivity.  One man’s meat is another man’s poison.  My absolute favorite mono cartridge is the 2M Mono SE, which is the mono version of the 2M Black.  I prefer it to a $2,000 MC that shall go nameless so as to avoid offense.  I prefer my 2M Black to any other sub $1K stereo cartridge that I own, although I have one of the vaunted Shure V15 Mr w/Jico deals and a very good Stanton 881 that are also better to me than any of the MC in that price range.  But that is my preference and it goes without saying that YRMV.  Just additional grist for the mill.  This question is like searching for the Holy Grail.

We are such a nice group of guys. No matter how open-ended and vague is the question, some of us will earnestly try to answer it.

I don’t think this is such a vague question, but I think it may be difficult to answer, since we all hear cartridges through our systems that have certain deviations from neutrality.

At level 3, I think my Lyra Kleos is pretty neutral, but when I compare it to a CD or digital high-res version of the same album, the digital tends to have more high-frequency content (and not always in a good, more musical way), so I don’t know if that means the Kleos or my phono cables are rolled off on top or if this is an artifact of my digital system.  (I have a Denafrips Venus 15 R2R DAC, and these are said to be pretty close to analog sound, and I think it is.) There may be some limitations from my tonearm, too, the Eminent Technology ET-2, which reviewers thought had less deep bass than the SME V, which was often considered a reference tonearm back in the day.

Do you mean to tell me the SME V is not still considered a reference tonearm?  I must be seriously out of touch.  Please define what you mean by reference.

You don't compare vinyl to digital, you compare it to master tape dubs. Deck's playback head is your reference "cartridge". Best decks', of course.

Generally speaking, cartridges are very coloured, aren't they ? Added colourations, negative colourations. In this sense they are often the weakest link, no matter how pleasing the sound might be. Koetsu appears to be a fine example of it.