Sheaths are a necessary evil, for sure. You need to make a sheath that's commensurate in value to the knife. If you're making rough $150 knives, you can get away with some yucky sheath work. If you want to sell a $400 hunter, you'd better have good leather, IMO. Whether you learn the skills or buy from skilled leather workers is a personal decision you'll have to make. I learned to do leather, although I find no joy in it. As it turns out, I typically end up doing leather in front of the TV, at times when I wouldn't be working on knives anyway. The profit margin is lower than for knife work, but I'm still making money in what would otherwise be idle time.