"There ain't no money above the fifth fret anyway..."
That quote comes directly from Mr. Chet Atkins. It was a joke. It later became a joke between him and Les Paul (I believe) on the Chester and Lester sessions.
The story goes like this:
A session guitarist was recording a solo for a song that Chet was producing. Being incredibly humbled that Mr. Atkins was in the studio for the session, the guitarist was playing all these "fancy lines". However, he could not find a solo that would fit. Seeing as Mr. Atkins was present the guitarist looked at Chet and asked, "what would you play there Mr. Atkins."
Chet's reply? "How about the melody."
The younger player marveled. Chet then added, "you don't need to play anything fancy. There isn't any money above the fifth fret anyway."
I am sure Chet had picked it up from Merle Travis or Joe Maphis, but it was coined as a joke with Nashville session players at the time who were embellishing simple solos WAY TOO MUCH. The producers would look in and say over the talkback, "listen son, there ain't no money above the fifth fret, why are you going up there anyway...."
Mr. Norman Blake still uses this line today. Johnny Cash used to say it often to him in his younger days. It is used as a line to calm down "busy" guitar pickers.