Elon Musk’s $1 billion purchase of Tesla shares sent the stock soaring this morning — along with his personal wealth. Bloomberg’s Matt Levine calculated that the share price rise thanks to Musk’s purchase was enough to raise the total value of his stock by $17 billion.

However, as Levine also pointed out, it’s not as if Musk will realize that gain any time soon:

“If you could spend $1 billion to make yourself $17 billion richer, and then cash out that $17 billion, that would be an amazing trade and you should do it all day long. But in practice, if buying $1 billion of stock makes your stock go up by $17 billion, then selling that $17 billion of stock will make your stock go down by much more.”