Niggas fantasize about the shit that I do daily
Like these rappers rap about all the shit that I do really
I'm like really half a billi nigga really you got baby money
keep it real with niggas, niggas aint got my lady's money
Remember wayne's song "a milli"? A billi is a play-on on that shit. Jay-Z is saying he has half a billion (a billi) because his estimated worth is 450 million. He's also saying Wayne doesn't have money because it's all Baby's (Birdman, Baby, Bryan Williams) money.
and since he also mentions beyonce, it's most likely one of the main reasons wayne mentions her too.
"do you fools listen to music or do you just skim through it?"