Action Comics No. 1 was the first superhero comic. In June 1938, this comic book introduced Superman. A copy of the comic book sold for $3.2 million in 2014. A copy in lower condition sold in 2018 for $573,600. A copy of Marvel Comics No. 1, Oct.-Nov. 1939, in mint condition, sold in 1984 for $35,000, and in 2001, one sold for $350,000. In 1991, a collector paid $55,000 for Detective 27, the first comic book in which Batman appeared. In 2010, another collector paid $1,075,500. Most of the high-priced comics contain superheroes. Price is determined by rarity and condition. Comics are graded and the record setters are 9.0 or above.