One of his most popular rookie cards is the 1990 Leaf Frank Thomas. Baseball cards in Gem MT 10 condition sell for roughly $35-$50. Cards in Mint 9 condition are worth about $15.50 each. Cards in higher grades increase in value. A Gem-MT99 card that is still intact with no signs of wear-and-tear can be worth up to $150. A near-Mint 100 card will go for more than $400. A complete set of major league baseball cards sold at retail price today would cost you around $40,000. However, many of these sets contain duplicates or other issues that reduce their value. An incomplete set with perhaps only 50 cards or less in it could be worth far more - up to several hundred thousand dollars. The highest graded complete set known to exist on record is the John McGraw Collection (JMC). It contains 833 cards and was purchased by an Illinois collector named Jerry Meyers for $383,000 in 2001. This is the most expensive card ever sold at auction. The next year, 2002, another complete set was sold at auction. This one went to a Florida collector named Bob Leafe and it was called the "Bob Leafe Complete Set". It too is grade-exclusive and contains 833 cards.