The authorship of Proverbs has not been easy to determine. Solomon's name appears in Proverbs 1:1, "The proverbs of Solomon the son of David, King of Israel", although this does not necessarily mean that he was the author. It was often the custom to place the name of the King or someone of prominence in writings in order to honour them, or to give those writings more prestige. However, Solomon is often mentioned as someone who has extensive wisdom in the Bible as well as in extra-Biblical literature. It is also said that people came from all over to hear the wisdom of Solomon. The general assumption is that Solomon was a part of the authorship to some extent, but that the book was not solely his work. There are also names linked to other sections of the book, as well as elements of disunity within the book that suggest more than one author.
No wonder the wisest man who ever lived, also became the richest!