https://www.cnet.com/news/spacex-will-help-nasa-go-crash-an-asteroid/

The total cost to launch DART is about $69 million (£53 million, AU$96 million). 

DART is designed to intercept a small moon of the asteroid Didymos in late 2022 when the rock comes within 6.8 million miles (11 million kilometers) of Earth. The spacecraft will crash into the moonlet, nicknamed "Didymoon," in an attempt to redirect its course.