Strait from their mouths.

Suddenly, in a matter of days, Montoya decided that "I'd rather race here and work with Chip and have fun than be there [on the global F1 tour] and not enjoying it."
Montoya will leave an estimated $14 million annual salary with the McLaren-Mercedes F1 team to drive a Dodge for Ganassi, who fielded IndyCars for Montoya in the U.S. in 1999-2000. His salary from Ganassi was not disclosed, but top NASCAR drivers average about $5 million a year in base salary and up to $10 million in endorsements.
That doesn't include merchandise. They make millions selling T-Shirts, hats, etc.