Assuming the knife is defective (and I have no personal knowledge on that score): In the U.S., in all fifty states, the general rule is that a buyer is entitled by law to be put in as good a situation as he would have been in had the product not been defective. That means the seller pays all costs of making good on the contract, refunds the full purchase price and pays for the return of the defective goods if wanted, or pays the buyer the cost of "cover" - buying a non-defective substitute. That is, the legislatures in all fifty states have decided that the burden of failing to deliver what is promised falls 100% on the seller.
I recognize that most sellers take a different position, and they hope you go along. The law is, however, quite clear.
The only way to avoid this libility is to clearly disclaim warranties created by law prior to the close of the deal. An example would be a notice in the advertisement as follows, "This new $250 knife is sold as is with all defects." "Fine print" inside the package that the buyer sees after the sale is entirely ineffective.
Practical considerations are, however, far from irrelevant.