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

At level 2, $1-3K, I have a Koetsu

At level 4, $5K+, I have a Koetsu Onyx and a Koetsu Leopard. 
 

Koetsu is not known for its neutrality, but of the three, the Leopard is most neutral. 

edsemble,

You are right these issues matter irrespective of source be it analog or digital.  

level 1 - up to$1k. - Shure V15vxmr

level 2 - up to $3. - Shure V15vxmr

level 3 - up to $5k. - Shure V15vxmr

level 4. - any price. - Shake Streamliner

Question: if a balanced and neutral cartridge was available in the lower price range, why would anyone pay more for one? (I suppose cynics would say for bragging rights.)

Seriously, if a cartridge is balanced and neutral buy it. My view is that there is probably no perfectly balanced and neutral cartridge, merely approximations that get more expensive as they asymptotically approach.

My solution is to enjoy the sound of each cartridge. I can tell which one I am listening to, and I like the choice of which to use when I select an LP.

I believe your solution is the correct one.