Apple's Beats buyout propelled Dr. Dre to the most profitable year of any musician ever

The rankings released this week by Forbes show Dr. Dre as far and away the No. 1 earner of 2014, earning more than a half-billion dollars more than the second-place earner, Beyonce. In fact, the top ten earners brought in $1.4 billion in pretax earnings last year, with nearly half of that from Dr. Dre alone.

Of course, the bulk of Dr. Dre's earnings didn't come from recording, performing or producing music, but instead from his entrepreneurial side —  specifically, the $3 billion sale of the company he co-founded, Beats, to Apple in May.

While Forbes didn't break down how much the Beats sale contributed to his 2014 earnings, it did specify that Dr. Dre's particularly lucrative year was "thanks largely to that deal." Apple's buyout of Beats also allowed Dr. Dre to make more in one year than any musician ever has in history.

Others on this year's list were legacy acts The Eagles ($100 million), Bon Jovi ($82 million) and Bruce Springsteen ($81 million). The only acts under age 30 to make the top 10 were Justin Bieber ($80 million) and One Direction ($75 million).

Before the Beats purchase was officially announced, Dr. Dre and performer Tyrese posted a video of themselves in the studio celebrating Dr. Dre as "the first billionaire in hip-hop." After the deal became official, Dr. Dre made a cameo appearance during Apple's Worldwide Developers Conference Keynote in June, participating in a phone call with software chief Craig Federighi.

Some industry watchers believe Dr.Dre and his Beats co-founder Jimmy Iovine were the main targets for Apple in the Beats acquisition. With Iovine's storied background in the music business and Dre's "cool factor," the pair could rejuvenate Apple's iTunes, which is seeing increased pressure from streaming radio services like Pandora and Spotify.