I recently bought a used Benz Ruby 2 from Wayne's Audio through US Audio Mart.
He stated he sells a lot of cartridges, he had several for sale, and good feedback. He was offering several vintage cartridges that he claimed have fewer than 50 hrs. use and he's marketing his own MC cartridge. He offered me a return privilege and installed the cartridge on my tonearm armtube. He also gave me credit for a used cartridge I sent him.
The cartridge was carefully packed and works fine. I've not felt a need to have it inspected, and I'm not sure there is anyone near me that would inspect it.
One advantage of buying a lightly-used cartridge from a trusted source is that it may be broken-in enough that you can judge how it will actually sound at its best; you can't always do that with a new cartridge.