Haha, I found it quite funny. I think it's coz he's posing with the money to make himself look rich, like a Rapstar, but he's only got $17. I'm asuming thats the irony? Anyway, I laughed.
Ironic? How the hell is this ironic? I'd think of irony if it said "17 and only $17" or something but WTF? Still wouldn't really make sense.
It sort of is ironic, because he obviously took the photo to show his gangster status p), and gangster is associated with lots of money, so he's tried to hold money to show he's rich, but its only 17 bucks.