I'm guessing it's cause of ze toobz. 10w isn't a lot, but if you're powering a small system, like a pair of bookshelf speakers in a small room, you might be in heaven.No se.
I also assumed it was more expensive because it'll play music from a phonograph player, which requires a special sort of preamp or something to increase the gain IIRC.
You might also be able to get away with something like this: https://www.monoprice.com/product?p_id=38360 if your phono has a built-in preamp (which many do these days). You could run the phono on the RCA, and the cd player on the optical. That's getting pretty complicated though, and I get the drive for simplicity.