Can anyone recall a fighter refusing a greater payday to make a more important (as in resume enhancing) fight?

For example - Mosley turned down around $12m for a third fight with Oscar to unify with Wright for about $2m.. but I believe the Oscar fight fell through because Mosley was demanding MORE than $12million. So wasn't really about Mosley looking to enhance his legacy.

For what reason - other than wonga - do pro fighters fight? Money drives every decision, no?