I like Karl's approach, and if I made knives that large (and certainly for that kind of money) I'd probably do the same thing, especially if shipping out of country.
Personally, I mostly make smaller fixed blades and folders, so usually they'll fit into a small priority box or similar. I rarely ship my knives without sheaths, but an any rate, I make sure there's no way that the point or edge could pierce free of the package. I also make sure that the knife isn't flopping around inside the package. I almost always have a pile of mailers/ad papers that I get almost daily in the mail, and these make great packing materials. Some times I'll even tape the wrapped knife TO the inside of the box for added protection.
Finally, the outside of the package is wrapped in tape such that no box seams are exposed, and the mailing label is printed and taped to the box. I always make sure to put clear tape AT LEAST over the buyer's address and my return address, so that if the package were to get wet, scraped, or whatever, the label is somewhat protected.
I've shipped dozens of knives and 100's of other packages this way, and have never had a problem.