Would you pay more than 25% of MSRP for a used cartridge?

I bought a DL 304. Used it 4 times, the fifth time I set it down the cantilever snapped, and Im very careful. I would budget a rebuild on any used cart purchase again, haven't made one since. 

Yes. I recently purchased a $5500 van den Hul Crimson XGW Stradivarius for $2100. The seller had 100 percent feedback with lots of sales and works at a local hi-fi store. The cartridge if fantastic and if it wasn’t, I’m sure the seller would have made it right, or worst case I could have sent it to Van Den Hul for a very affordable rebuild.

Another time I bought a different Van Den Hul (MC Two Special) and when I received it there was no diamond on the cantilever. The seller (a trusted dealer I have purchased from many times) gave me a full refund and I sent the cart Van Den Hul and had it rebuilt.

I also got a great deal on near perfect Soundsmith Aida II, which again could have been sent to Soundsmith for an affordable rebuild in the worst case.

There's also Andy Kim.  I bought a turntable that had a Zu Denon DL 103 on it, which sounded horrible.  I sent it to Andy and he confirmed that it had a number of issues on it.  After he worked his magic, it is now my 2nd most favorite cartridge at a fraction of the price of a number of other carts I own.

Even in the worst case, with many carts you can have a like new cart for half or less the price of a new one if you're willing to have it retipped.

I did something similar with a Shure V15 that I bought with a broken stylus.  I bought a JICO SAS and voila', a great MM for little money.

I would only consider upto 50% MSRP for used if:

1. The cartridge is a current model and no more than 1 year old. I don't want some old thing sitting around for years.
2. The seller was a retipper or had extensive feedback from selling similar kind of cartridges.

Otherwise I will just assume it needs a retip and not worth more than 25% MSRP.

Here’s where everyone trots out his or her individual experiences buying used cartridges. As to the issue of cost, I forgot to point out that many cartridges that are out of production are now valued much higher than their original MSRP. For those cartridges, there is virtually no relationship between the used value and the MSRP. In my opinion, it’s foolish to make a hard rule about what the valuation of a used cartridge should be in relation to its MSRP. Each case is unique.

12inch, you have no idea what you’re missing if you completely rule out “old things”.

Agree with most that used cartridges are too risky to buy. Many dealers will give you 20% discount so just buy new.