At what price point do I run into diminishing returns on an MC Cartridge?

I need to replace my MC cartridge.  I've had limited experience with them but I have certainly noticed a dramatic difference in performance.  My first 3 were priced at $500 Sumiko, $900 Ortofon and $5000 Linn Kandid.  The difference between my first cartridge and second - nearly double in price, was a very noticeable improvement.  Then I took the plunge and spent $5000 (after tax) for my Linn Kandid cartridge.  The difference and improvement in the quality of sound was startling.  The soundstage was like nothing I'd ever heard before.  Coupled with my newly acquired McIntosh MP 1100 phono pre-amp and I was hearing things in LP's that quite frankly I had never heard before.  Amazing!  So here's the question: At what price point do I run into seriously diminished returns on a cartridge investment?  I rather doubt I'm going to have "double" the quality of sound that I received with my Linn Kandid cartridge if e.g. I went up to a $10K cartridge. So, my question to you audiophiles with loads of experience, what is your opinion on what price point (neighborhood) would take me to a place where every dollar spent thereafter would yield only micro returns.  Said another way, what is the best price point to take anyone to the the same neighborhood as a person with "money to burn" on cartridges?  BTW, I realize there are probably some pearls that don't cost nearly as much - and that money doesn't always buy you love.  If you KNOW of those do tell.