Dr Dre – or Andre Young – hasn't released a new record since 1999. And his next rumoured release, Detox, has been pushed back so often that it's beginning to look like the hip-hop world's version of Guns N' Roses' Chinese Democracy. And yet in a new Forbes report, Dre is listed as the highest-earning rapper of 2011, raking in a massive $110m (£69m).

But how?

Beats headphones. His investment in Beats by Dre, which sells stylish headphones for up to £350 a pair, accounted for more than 90 per cent of his pre-tax income. The money he made from his headlining Coachella set – which featured a digital projection of Tupac – is just pennies by comparison. And expect his 2012 earnings to be even higher. His headphones managed to navigate the rigid ambush marketing laws at the Olympics so successfully that at times it seemed as though Beats was the sole official sponsor. Michael Phelps blocked out the Aquatic Centre noise in his Beats, Chinese swimmer Sun Yang colour-coded his Beats with his red jacket, and Tom Daley tweeted his delight at receiving a free pair.

Doesn't that make him a sellout?

If you believe it does, don't seek out a copy of the full Forbes study. Diddy, second, took $45m (£28m), mostly from an investment in Ciroc vodka, while Jay-Z, in third place, rakes in cash via partnerships with Duracell and the Brooklyn Nets. At five is Lil Wayne, who has a big-money deal with Pepsi, and in tenth is Ludacris, whose interests include Conjure cognac and headphone line Soul.