Experience purchasing a used high-end cartridge

I don’t do it. Too many vulnerabilities with cartridges. And while I have had many excellent retips done, the sound is never quite the same as original, IME. If you have the option of having a manufacturer do a rebuild of the purchase, which is essentially a new cartridge, with warranty, then maybe. But at that point the costs mount. I’d rather save up and buy new, if only to quiet the doubts in my mind. And I consider the cost and availability of manufacturer rebuild as a condition of purchase. It’s one reason I own no Zyx: rebuild costs are too high. Ortofons, though, are reasonable.

All that said, I did recently buy, at a steep discount, a demo MC Diamond that had been used at Axpona. But it came directly from Ortofon with full warranty and had less than 20 hours on it. I trust Louis at Ortofon USA, so I had no worries.

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.