The slow end of President Trump's relationship with Elon Musk, which occurred on Thursday, cost both men significant amounts of money.

Why it matters: Both own massive business empires, but each has one public company, and investors abandoned both when their social media war turned into personal attacks.

In numbers: Tesla's stock fell by 14.3%, costing Musk just under $20 billion.

The drop in shares of Trump Media & Technology Group by 8% cost the president about $202 million.

The biggest hit to Trump's earnings was the approximately 10% drop in the value of his meme coin 'Official Trump', which could potentially cost him nearly $900 million.

Summary: Both men publicly expressed their frustration, and it cost them only about $21 billion.