It is a Free Market Economy. America is a Capitalist country. The people that sell the raw materials to the Factory add a margin to their cost. The Factory has to sell at a profit to stay in business. Etc, Etc. I know you are talking about a private individual "flipping" a knife. But my point is that profit is the motivation for a lot of this whole thing. I'm sure people make knives because that's what they love to do, but they don't do it for any altruistic motive, they do it for profit. A lot of Collectors collect what they like, but also hope that their collection will become quite valuable in the future. As for the flippers, no one is forced to buy a knife at all. If an individual is willing to pay a certain price to obtain a certain piece, so be it. It is their decision. Why would anybody pay thousands of dollars for a certain Silver Dollar? It's face value is One Dollar. It contains about $15 of silver. Yet Collectors pay incredible prices for a certain piece, certain mint mark, certain condition.
You can sell your knives any way you want to. You can buy your knives the way you want. So can everybody else.