If I'm correct, that list is from encycolpedia.com or something. There are MANY mistakes on their pages.

I don't think Def Leppard has sold 90 million albums worldwide. They had 2 really big albums globally - Pyromania and Hysteria. That list claims that Slang and Euphoria both sold over 10 million worldwide - Not even close.

I'm not certain of Metallica's numbers, but I can't imagine they've sold twice as many albums as Bon Jovi. Theoir global following isn't nearly as big, and they've had many duds for albums.