Yeah, it’s a total mystery.

Via RCP:

JONATHAN KARL, ABC NEWS: The First Lady had her 50th birthday party and I believe you said that the president picks up the cost for that party?

JAY CARNEY: I think we put out information on that. I don’t have it here. I refer you to the East Wing.

KARL: I was just wondering if you have an estimate on what the cost was?

CARNEY: I don’t, but I would refer you to the East Wing.