The host of Project Farm compared the results of using a bunch of different knife sharpeners ranging in cost from nine dollars to $900. It turned out that the $9 sharpener was pretty good. His favorite was the Lansky sharpener, which costs about $45.
From the YouTube description:
Knife sharpeners tested: Lansky, Wicked Edge Gen 3 Pro, Spyderco, Fiskars, Rada, Chef's Choice Trizor Edge, Model 15XV, Edge Pro Apex, and a Whetstone. Knives used for testing: Mercer Culinary Millennia 8-Inch Chef's Knife, which were dulled, then sharpened using each knife sharpener. Stropping leather used on knives sharpened with Lansky, Wicked Edge, Spyderco, Edge Pro Apex and Whetstone. Once sharp, knives were tested using a knife sharpness tester.