The 45 Cent Concert

Okay, listen up, dummy. You see, 50 Cent is a rapper, and Nickelback is a band. The joke is that if you get 50 Cent to perform with Nickelback, it would only cost 45 cents. Because, you know, it's "50 Cent featuring Nickelback", so it's 50 minus 5 (nickel) which equals 45. And the perceived low quality of Nickelback's music suggests their presence would devalue the concert.