Dr. Dre hasn't released an album in 13 years ... and at this point, he might never put another one out again.

That's because the Good Doctor tops Forbes' new list of "The World's 25 Highest-Paid Musicians," raking in an estimated $110 million from May 2011 to May 2012, when the magazine looked at revenues. Dre's haul dwarfed the likes of Britney Spears, Taylor Swift, Justin Bieber and Kanye West, all of whom made the cut, and was nearly $30 million more than the man who came in at #2 on the list, Roger Waters.

And, as you are probably aware, he made all of that loot without releasing a single note of new music (his last single, "I Need A Doctor," hit in February 2011). And while royalties from his expansive back catalog and payment for performances like his [article id="1683143"]headlining set at the Coachella fest[/article] certainly helped fill his coffers, the majority of Dre's wealth these days comes one very profitable source: his range of Beats headphones, earphones and accessories.

Dre founded Beats Electronics with Interscope/Geffen/A&M chairman Jimmy Iovine in 2006, and the company produced the first set of Beats by Dr. Dre headphones in late 2008, and while the profits were certainly there, he really cashed in last August, when Taiwanese corporation HTC purchased 51 percent of Beats for a reported $300 million.

According to Forbes, that purchase netted Dre a cool $100 million, and, less than a year later, HTC decided to sell back half of its stake to Beats (though they still retain exclusive rights to use Beats Audio technology in their mobile devices). Dre and Iovine have only continued to expand their Beats empire, creating a line of boomboxes to go along with their headphones, and Beats speakers can also be found in the Chrysler 300, the Dodge Charger and a line of HP laptops, too.

There are also reports that Beats is branching out into the smartphone market, with a line of devices manufactured by HTC, and making preliminary moves towards launching a custom Beats television, partnering with a manufacturer to create "an Apple-like experience that extends from a phone to a TV to a tablet to a laptop ... much in the same way Apple does with Apple TV, AirPlay and iTunes." Beats also acquired online music service MOG this summer, for a something in the neighborhood of $10 to $16 million.

Of course, at the end of the year, Beats' five-year deal with Monster Cable Products -- which was the exclusive manufacturer of their headphones and speakers -- will come to an end, meaning that the company will go forth on their own ... certainly a risky move, but, given they control a reported 53 percent of the $1-billion-headphone marketplace, one that could pay even biggerdividends for Dre.

Like we said, at this point, who needs Detox?

Should Dr. Dre focus on the boardroom or the studio? Let us know in the comments below!