Ink by the barrel

A wise man once advised me to 'never get into a public argument with anyone who buys ink by the barrel'--- or paper by the trainload!. I can't find an origin for this wise advice, even though I've heard it a great number of times in my career. Any help?

I couldn't find it in any of my quote books. Online it was called an "old adage" on one site. On others it was attributed to Oscar Wilde and Mark Twain. Still looking.