The big power cord? It's not a 10/3, it's just a tiny 18/2.
I'm well aware that no audio is truly wireless. Like I stated in my first post, I was a Sonos dealer for years, offering their products alongside hard-wired centralized systems from just about every manufacturer; Elan, Savant, Control4, Russound, etc.
Is Sonos better than hardwired, centralized systems? Maybe, maybe not. Is it better for the end-user? That's up to them. But audio performance is just one facet of the equation for end-users these days, along with convenience, cost, aesthetics, ease-of-use and reliability. If those weren't real world concerns for millions of users, then Sonos, MusicCast and Heos wouldn't exist. However, in that space, Sonos is the big player and the biggest reason has been their App. It just works and users enjoy that, albeit at the expense of better fidelity that may be offered by more complicated systems that users deem unnecessary in their own minds.