What is so special about Audible recordings that is unnattainable by Librivox? You mean sound quality? You mean some holy grail vocal mics? Or vocal talent? I don't get it.
I've listened to a few Librevox recordings. They're usually (though not always) tolerable. Occaisionlly good, but that's exceeding rare.
Good audiobooks -- and a friend listens to many -- are far more often vastly superior. Even then, a poor reader is exceedingly grating.
Libravox may improve with time. History of volunteer efforts has been compeling. But not yet.
I'm impressed by what librivox has achieved with just volunteers, but the production values are nowhere near as high as most books on audible.
IMHO they are just doing injustice to a number of good readers in their catalogue who put real effort into their recordings, but get buried under those one can barely listen to.