I bought a KS in '11 for $150. Had Mike Henry install a handle, and had a saya made for it. Think I sold it for $250. I loved the profile, but I do remember thinking it was rather soft, and seemed to melt on the stones, and I have a very soft touch when sharpening. I think the profile also lends to needing thinning quickly, as well as risking creating an unwanted flat spot, and achieving accordion cuts. So, not a profile for beginners.
Now more recently I have had in a few of the newer batched KS in the shop, and can say, they are not the same knife I remember. They seem to have no soul. Everything is a little squarer, more machined, crisper. So, take the original quarks, and add some new ones, and I'm not so sure why the KS is again so popular.
There have been many KS clones, and I have liked many of them more.