Those types of handles (and blades) are usually waterjet or cnc cut, or hand filed/ground, I'll make an educated guess that the esee stuff is waterjet, like most.
Cutting complex asymetrical curvature on a mill is very difficult, and usually bad news for your cutters, which want consistency in feed. I've tried it, since I like totally skeletonized tangs, and personally have found it easier to rough with drills, or make a rough slot with the mill, and then finish with carbide burrs and hand files.
That's probably the easiest for one-off designs. A cnc mill would be the next option. For any reproduction, waterjet seems the most economical option. Don't expect to be doing it with a small mill like the ones discussed in this thread.