The Gil Hibben knives always cost more; he is a very well-known knifemaker even outside of the typical knife collector circles. He's done a very good job at marketing himself, his name, and his knives.
I'm sure the Made-In-China production models will be much less expensive, and available at Mall Ninja Knife Stores everywhere.
Regarding the actual knife design, it's not much to look at. And yeah, that's a ridiculous sheath.
Maybe the knife design origin is worked into the movie plot somehow? Like this:
A native boy is forced to throw out a United Rambo III knife, because of his father's anti-communist political beliefs. John Rambo finds it in the dumpster and hammers and grinds it into a new knife. Now he needs a sheath, but the only thing he can find quickly is a Tromontina machete sheath that someone has discarded because a dog ate the end of it...