I think that mabey the OP asks the wrong question. Of course prosperity is a blessing, but not knowing how to handle it can certainly be a curse.
Of course, I have never had that much money, so I cant really put myself in his shoes.
But I do know this. The Bible says that children are a blessing from the Lord. But even today people sell there children into slavery, poeple had committed suicide because they cannot provide for their children, and we even know from stories in the Bible that poeple have killed and eaten their children.
One could say, are children then always a blessing? Of course they are, but not knowing or following Gods principals for raising them can be a curse.
Money is a tool, and is not inherently good or evil. It is the state of ones heart, and what they do with it that makes it a blessing or a curse.
Peace...