In any case, you don't pay $4 billion for $4 billion in assets. You might pay $4 billion for $4 billion in potential profits, but not for assets. They can hope to make $1 billion or so (rough, rough, estimate) from their $4 billion in assets. Nobody is stupid enough to buy $1 billion profit potential for $4 billion. Aurus wouldn't even be able to get that kind of credit in the first place.
It would make a hell of a lot more sense if they paid $100-$200 million for the mining rights, which they did.
Think about this rationally before you throw ideas like that around.