Just like in most other things, there is a point of diminishing returns in the custom knife area. Once you pass $300 for a knife, you are either paying for a name or very exotic materials, IMHO. And there isn't anything wrong with either. When you go custom for anything, (guns, knives, etc), pride of ownership should play a big part in the choice. Granted there are knives that are works of art, and very expensive to boot, but they are for looking, not using.
There is no way that I'd pay more than a couple hundred, maybe $300 at the top, for a using knife. I'm hard on equipment to begin with, but I can't see how having more money than that invested in a knife would make it better for ME. There are others who would disagree, I'm sure.