Build a man a fire, he will be warm for the night. Set a man on fire, he will be warm for the rest of his life.
Preppers would be better served by spending their knife money to buy the tools needed to make a knife, and developing that skill. Buying a knife doesn’t make me stronger, smarter or more skilled. Building a knife does, and provides me with a useful and negotiable craft. Knives are maybe the oldest of tools-axes and hammers might be older, and don’t need to be CNC machined out of exotic steel to be useful.