You’d think the “Material Girl” knows how to tip her servers well and at least be polite when dining out, since she’s been in the business for so long. Wrong. Sources say that Madonna once paid an $18 tip for a bill that was around $400. That’s pretty disappointing, to say the least. However, we can’t say we’re too surprised. After Madonna’s recent (and extremely inappropriate) kiss with Drake at Coachella and her desperate attempts to prove that she’s still “got it” by wearing corsets and fishnets on stage, it’s no shock that Madonna still has a lot to learn when it comes to social graces.