"Screwed" is a state of mind. No one buying a knife on the secondary market is getting screwed, because every single one of them wants to do it. And when someone wants to do something, it can hardly be said that they are screwed. A person is screwed only when he wants to do something and cannot, or is forced to do something he would like to avoid. Secondary buyers don't fall into either category because they are acting in concert with their desires.
I have no problem whatsoever when someone makes money by flipping a knife. That is exactly what vendors are doing too - buying from a 3rd party, raising the price, and selling it. Everyone is free to 1) pay close attention and buy limited edition knives while they are still available, 2) buy to flip, 3) buy from a flipper or 4) none of the foregoing. Laissez faire baby!