My guess is that they need to be cut using EDM (slow) and need expensive CMM machines to make sure the resulting die shapes match the tolerance.
I know you're probably referring to OEM hand crimping tools that cost on the order of 500€/$, but even decent quality non-OEM tools (e.g. Engineer PAD-11) aren't exactly cheap. Though, I hear IWISS ones are usable if you're on a budget.
The generics are pretty cheap, but I guess it's a relative matter. I got a PA-20 for $35 on Amazon and it works with all the Molex micro-fit I've thrown at it. Each crimp takes much longer than if I had the $500 purpose-built tool from Molex itself, but I do so few it doesn't matter.
