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The most expensive typo in history

The world's most expensive typo is generally considered to be a mistake in Mariner 1's guidance system. (Mariner 1 was a probe constructed by NASA to take photos of and gather data from Venus.)

In 1962, shortly following its launch, Mariner 1 was destroyed when a mistake in its guidance system's algorithm sent the rocket off course—and directly toward North Atlantic shipping lanes.

After Mariner 1's crash, the cause of the faulty algorithm was determined to be a missing overbar, which is a line placed over text. Despite the seemingly small size of the overbar, its inclusion in the guidance system's algorithm was essential.

The cost of this typo, when adjusted for inflation, has been estimated to be around $150 million. In addition to the monetary cost, NASA's failure damaged the organization's credibility, and the world was forced to wait a bit longer for up-close pictures of Venus.