Not chump change to a guy who makes $100,000,000 a year? It would be analygous to $15 to someone who makes $100,000 a year. He makes $15,000 just to show up to a tournament.
Some of the foreign tournamants pay him hundreds of thousands, even millions just to show up.
This year, he was paid 4.5 million just to show up and play the Australian Open.
15K hooker sprees + their performance bonuses (jewelry, purses, clothes, etc..) once or twice a month is chump change to him.