I've only heard of poor experiences buying Benz cartridges (supposedly NEW) from a Hong Kong dealer in Hong Kong. I can't imagine that regulars would dare pass off trash here.
Buying used Cartriges
I quick gander at the classified section here on A-Gon will reveal that cartridges sell very well. How do you all protect your selves in buy something that you cannot verify the age and condition of? The sales are not being made with long term, high feedback members. Many are zero feedback users. Most sellers state, used "50-100 hours", with models that have been on the market for several years. I have made 3 cartridge purchases here on Agon and have been lucky so far, but am in the majority or minority?