I have bought at least 8 used cartridges. I only buy where the seller specifies his usage and I discount that heavily. So if somebody says < 20 hours I assume it has at least 50 on it. I would almost never buy a cartridge where a seller claimed more than 100 hours unless it was very deeply discounted. I did make an exception for a Koetsu Urushi Gold I recently bought where the seller claimed 250 hours but the price was good and it is impossible to buy new Koetsu's anymore. My only disappointment was a Soundsmith Zephyr MKII and I really have no idea if the seller misrepresented it or it just is a bad cartridge.
Unless you have a lot of money the only realistic way to try a lot of cartridges is to buy them used. Lots of vinyl junkies have multiple cartridges which does mean there are many genuinely low hour cartridges that might come up for sale.
I would never buy a cartridge that was retipped or where the user claimed "only 500 hours and it still sounds great". Diamonds aren't forever when it comes to cartridges.