I'm not necessarily defending their high price, but a lot of these balis have a huge amount of titanium on them....
I'm not sure that locks are really a big addition to cost....take the expensive compression lock for instance...it's exactly the same as a liner lock on the back, except much more expensive (I like it a ton more and am willing to pay it, but the design shouldn't cost anymore). Perhaps it's the small production numbers...
Benchmade balis are borderline hand made quality in my opinion though. They're gorgeous. When I spent my 140 on my 41MC and compared it to a 120 710 (another great knife), I really have to wonder why the 710 actually cost so much, not the 41MC.
But ultimately, yeah, they could definitely be cheaper. Check out the spyderfly, 70 bucks, spyderco, I have some problems with mine, but mine is still reliable, smooth and fun regardless.