Not sure if it's always been this way, maybe I just noticed it. But after the race it'll say,
"Race Objective: Finish 1st
Prize: $0"
Now, I get if I finish 2nd or below the objective is failed (though it still displays a green check mark), but when I finish first it still says, "Objective 1st, prize: $0".
After the race, when I go back to the main menu I'll collect xp, reputation points and my prize money, but it seems like maybe a bug that the popup in the race screen tell me I get zero for completing the objective.