Explore the 30 Most Valuable Baseball Cards Defining A Collecting Era Top Picks Rare 1969 WILLIE MAYS Signed Topps Baseball Card HOF GIANTS PSA 9 Auto Two siblings found this rare baseball card inside a Target blaster box Domingo Caraballo and his brother bought the box at Target, and upon opening it, found this Barry Bonds autograph Houstonian's rare baseball card could fetch $1.5 million