For the most part, Apple TV channels seem more about organizing your streaming media, rather than giving you something new. Apple pitches it as an alternative to services like Sling TV and PlayStation Vue, which offers bundled cable TV channels. By offering an a la carte alternative, it could save some viewers money. Of course, the participating networks also have their own Apple TV apps, but jumping between is not as hassle-free as the channels would also solve.
Apple doesn't offer any price information yet for channels, but rumors point to $ 1