I've bought and sold a few. I think a fair batting average is about 75%, but in the worse case scenario, I think if the motor is in good shape, Peter Ledermann (Soundsmith) can literally fix any cartridge and make it sound better than new. I sent him a used Maestro which lost its diamond, and he sent me back the cartridge with a ruby cantilever and a shibata type stylus. Best MM I've ever heard - much better than even the Maestro V2.
Used cartridges I've bought that were perfect - a Miyajima Shilabe and a Shelter 90X. Used cartridges with problems - a Koetsu Black and the afore-mentioned Clearaudio. You pays your coin and you takes your chances, but it usually works out in the end.
Used cartridges I've bought that were perfect - a Miyajima Shilabe and a Shelter 90X. Used cartridges with problems - a Koetsu Black and the afore-mentioned Clearaudio. You pays your coin and you takes your chances, but it usually works out in the end.