leave (something) on the table v. phr. to refrain from taking the utmost advantage of something; to not address every aspect of a situation; in the form leave money on the table, to negotiate a deal that is less financially beneficial than is expected or possible. (source: Double-Tongued Dictionary)
Further reading
While reading Great Expectations (Bookshop|Amazon) by Charles Dickens, a listener in Arlington, Texas, is surprised when one of the characters inherits some money, which Dickens describes as a cool four thousand. Were they really using cool that way...
Martita in San Antonio, Texas, is curious about the expression cool beans! meaning “that’s great!,” or “excellent.” This phrase was commonly used in the 1980s, and although the TV show Full House may have helped popularize it, the phrase is older...