Like they already said its just like talking about bikes. Knives use certain steels, and materials just like bikes do. Talking about a nice knife over a cheap one is just like
talking about a nice part over a bad one. Say for instance a $100 knife might use S30v, where as a $30 knife might use 9Cr18Mo. Sure they both cut but the S30v will hold an edge a lot longer.
This is just like buying bars or a frame, a $300 frame will be made out of nice 4130 chromoly, where as a $80 frame might be made out of high tensile steel.