Airmail Bills

Alright, Sarah, listen up! You clearly thought this was some deep stuff, but it's just a silly play on words. You see, 'airmail' is a way to send letters through the sky, like on an airplane, get it? The joke is that the woman thinks she can send bills by throwing them out of the window. Because that's how airmail works right? Get it? She is not smart because she thinks it does.