Sharpening knives by hand is a long time hobby of mine. Like people said, $1 per inch is standard, but really depends on the quality. It also depends on how sharp a knife you'd like. If you truly don't need or want shaving sharp, then he may be ok. A cheap knife like the kiwi brands are poor quality metal that is just very very thin, but the cutting edge is not as sharp. Because the metal is so cheap, they are easy to sharpen to a "scary sharp", but will not hold that edge for very long at all. Give him an old knife you don't care much about (but not a tiny $3 one either) and see how he does first before bringing all your knives. I'm amazed at how many "professional" knife sharpeners with belt rigs and all have no idea what it means to have a sharp knife.