Experience purchasing a used high-end cartridge

I don’t know how anyone else’s experience could bear on your decision, unless you unearth another person who bought an LOMC from the same source. If you’re really insecure, ask the seller if you can have the cartridge inspected by a trusted retipper, at your expense and in advance of any sale. If he doesn’t agree to that, you may have your answer. If he does, you’ll know exactly what you’re getting.

Not within the last year, but I bought a used Denon LOMC and have (knock on wood) no issues whatsoever.

I'd never buy a used phono cartridge.

There are a number of good re-tippers out there,  many original manufacturer have rebuilding services. I would not worry too much specially if the price is reasonable so when you add the rebuilding cost its still a good price.  

I recently bought a Sumiko pearwood celebration 2 at well below 50% cost, its sounds great and at the price i can rebuild it and still be below the used price market. 

Like I said, trust but verify with an independent expert.  I'd go that route without a second thought.