Worth pointing out that he has also lost net worth as a result of the midterm loss. By about $25 billion.

As others point out he doesn't have cash to hand like this, that's not how net worth works. It's also a pyramid of smaller investments from other people in effect. And investors watching a guy sink almost $400 million into something and failing to get the result they want, and making a 60x loss on it, will reduce their faith in that person to make money on their behalf.

Now, Musk's companies fluctuate near to this scale daily, at this value there's no way they don't. But, this will make it more likely that those companies make a similar loss on day's when Musk is shown to be behind a big decision - if investors do see this as black mark on his decision-making.

So, it's pretty huge deal that really does matter.