I heard on sports talk radio last week from the father of NBA player Klay Thompson that he receives his son's pay check to manage his money for him. The father, a former NBA player himself, then pays his son's fixed expenses (no mention of how much) and then gives his son an allowance of only $300 per week.
His son, Klay, is 23 and makes $2.2M per season...he's good to and will probably end up making $60-80M or so over the course of his career.
Given his extremely high income level I think "only" having $1200 a month in discretionary income is very mustachian for young Klay.