(Proverbs 11:22 KJV) As a jewel of gold in a swine's snout, so is a fair woman which is without discretion.
Humor is often based on the unexpected. This is a form of humor that makes a point. We have two contrasts based on the weakness we have to judge a book by its cover. Sometimes it works. Sometimes it doesn’t. If I am checking out a tall stack of books from the library I can afford to get a few wrong. If you are buying a book for a long ride on an airplane you might want to look little farther than the cover.
I am sure that somewhere in the world there is a pig with a gold ring in its snout. I doubt if it will effect the quality of the bacon produced. The point is that precious gold does not change the stereotype of unclean animals into something blessed by God. In the same way, outward beauty does not make up for lack of character in us humans. Not being one of the beautiful people I have no trouble with this.
So? After looking at the cover, dig a little deeper. In selecting friends or spouses keep in mind that the gold ring still has value but the worth of the beauty is questionable.