I just had a guy over to buy a couple of cheap knives. He could not afford the more expensive ones, but even as an inexperienced person, and just a "normal knife user", when I laid them all out he could instantly tell the difference in quality. Not even knowing what the materials are, he kept commenting on how much better the more expensive ones felt and how smooth and strong they were.
Hold a $200 Emerson Commander or Microtech next to your choice of lower line folder, and if you don't see the immediate difference, then please put it down and don't buy it
There is a point where you are getting less for the price point...much like buying a rifle for $1000 that will shoot 1 moa, but then spending $3000 for a rifle that will shoot 1/2 moa. By the numbers there is a very little difference in performance, but to an avid marksman, they would not think of being cheap and buying the $1000 rifle.
Custom folders are in a league of their own and once again, when you feel a $400 Kit Carson or Greg Lightfoot folder next to a $200 Microtech or production Emerson, you will notice a difference, but it is up to you whether that difference is worth twice the cost.
Personally, I think there is a point where you are losing ground, and I tend to stick with the $200 range of folders, most of the time. But that is because I am a college student, and that is all I can afford to USE (rather than look at). If/when I make more money, a $400 folder would not be out of the question to use. As it is, when I am betting my life on a knife, I still use a $350 Mad Dog fixed blade, but for folders which usually don't get as hard of use, I get by with the $200 range.
Same anaolgy regarding fixed blades goes for Mad Dog versus Cold Steel. The Cold Steel Bush Ranger will get the job done most of the time, but those of us that strive to be professionals and want to be able to put our life on our knife, pay four times the cost for a Mad Dog because we KNOW that we could cut our way out of a burning car with it if we had to, among many other high quality features of the Mad Dog line.
A knife is your first resort tool and your last resort weapon. Make sure that when you reach for it, it will put up with whatever you can dish out, because you life may depend on it.