Why is that stupid?
If it would be wrong for the retailer not to pay to have the lens fixed, why would it not be just as wrong for you not to pay for having it fixed for the next owner? The retailer sells Canon because they have a reputation for making high-quality camera gear; you're selling that particular lens because you think it may break again in the future and you don't want to be stuck with it when it does. Will you be telling the prospective buyer that it already broke once and you're afraid that it will break again?
It is stupid because retailers are governed by Laws such as the Consumer Guarantees Act, the Fair Trading Act, where legally they are bound to certain rules, the brand name means nothing under the law.
The retailer in my opinion doesn't sell the product because "they have a reputation for making high-quality camera gear" they sell many brands of camera gear and other consumer goods to make a profit.
I've decided not to sell my lens because frankly there is nothing else on the market with the same versatility, I'm hopeful that Canon replaced the part with a superseded part as it's well documented that there is a problem with the IS system on the 100-400.
If I was to sell it I would advertise it in it's current condition on TradeMe (similar to eBay)
and I would answer all questions honestly.
