It's really no surprise that Madonna has been named the top-earning celebrity of 2013 by Forbes magazine.  After all, she joined the billionaire's club earlier this year.

In the spring, the pop star, 55, became a part of an elite group of people whose bank balances surpass a whopping $1 billion. She earned approximately $125 million alone between June 2012 and June 2013.

The singer's record breaking "MDNA" world tour grossed more than $305 million last year. She also earned $75 million from concert merchandise and $10 million from TV rights and DVD sales.

Investments in her Hard Candy gym franchise and coconut health drink Vito Coco, as well as a $10 million deal with Smirnoff vodka, increased her personal fortune.

There's more.

Madonna's "Truth or Dare" perfume has earned $60 million in sales, while her Material Girl clothing and accessories line is expected to draw another $10 million in 2013.

She's a woman who knows how to market herself, and the result is big bucks. Celebrities (whether actors or musicians) must do more than just perform their craft in order to earn a hefty paycheck.  To be truly financially successful, stars must become a brand. Whether it's selling clothes at Kmart (Selena Gomez) or pumping out fragrance after fragrance (Beyonce), many do whatever they can to fill their pockets.

We don't blame them. What would we do without Justin Bieber nail polish?

Check out four other celebs who made big bucks over the last year...