Well, if I would've used a knife for quite some time, I probably would've not minded paying for shipping (actual local shipping) both ways. I could also estimate how much wear it would take before the next time and would vote with my money, if I'm OK (or not OK) with the terms and overall cost of the knife.
The problem I see here is that some manufacturers charge $14 and call it "return shipping", though USPS priority to any USA destination usually costs half of that even with insurance. As a matter of fact, if it was a cheap knife, it might as well be that manufacturer is selling you another knife at the factory price without overhead costs.
Also, some manufacturer's tend to approach quality control issues the same way as warranty repair. I don't mind paying for warranty repair shipping, but as far as quality control issues, I want the manufacturer (or distributor) to pay even for my end of the shipping, because NEW knife should be free from defects and it is their problem, if it was not.