How much is the wages for pro motocross riders?

It depend on a number of variables, the sponsors and number of sponsors, the contract they signed, and more importantly, "How good they are" Bonuses can/could be paid for hole-shots, wins, places and so-on. The more wins they have, the more valuable they become. Ricky Carmichael had a contract with Honda for 2 million dollars a year. So if they are good enough, the monies can be substantial.