What Tennis Stars Are Really Worth.

It's January the Australian Open is in full swing and that begs the question, how much do tennis players actually earn? According to the article below, quite a lot.

What tennis stars are really raking in each year?

Earnings data for 2013 was sourced from the link below.

http://www.forbes.com/sites/kurtbadenhausen/2013/08/26/endorsements-fuel-the-worlds-highest-paid-tennis-players/

The players' career history (including all earnings over their career) can be found by searching for the relevant player on the Australian open website.

Australian Open Player Biographies

Are the figures quoted in the Herald Sun news article accurate?

If we were to assume that Roger Federer has earned his prize money at a constant rate from the time he became a professional tennis player to today, how much money would he earn per day?

Is this a reasonable assumption? Why or why not? What factors can affect the rate that he earns his prize money?